Did you know that the problem of low power factor in the electrical installation – which can lead to fines from the energy concessionary, can be solved with the installation of power factor controllers?

Look at your electric bill. If it shows excess reactive consumption, this is a sign that there is a problem with the power factor. The further this consumption deviates from the legal value, the higher the fine imposed by the energy provider.

This is where power factor controllers come in, to help you correct this flaw in the electrical installation. Before presenting the types of power factor controllers, it is necessary to understand what power factor is.

What is power factor?

Power factor (PF) is a measure of how much of the electrical power consumed is being converted into useful work. The minimum allowed power factor on the energy bill, according to National Electrical Energy Agency (ANEEL)is 0.92. If the value is below this, the utility can charge a fine, as mentioned above.

The main causes of low power factor are discharge lamps (fluorescent, mercury vapor, sodium vapor, and metal vapor) with low power factor reactors (without capacitor), transformers at no load or low load, and induction motors (motors most commonly used in industry).

What a power factor controller is and how it works

ST8200C Power factor controllerPower factor controllers measure the voltage and current of the load continuously, calculating their values through mathematical algorithms in order to obtain TRUE RMS values. Calculated in this way, the power factor considers the harmonic content of the current and voltage, resulting in more accurate measurements.

Optionally, the power factor can be obtained via the serial interface of the power electronic recorder (REP) user output. In this case, there is no harmonic calculation.

As needed, that is, whenever the inductive power factor falls below the setpoint, the controllers activate one or more capacitor banks, thus providing an efficient correction.

The controllers have several features whose purpose is to protect your investment in capacitor banks. Among them is the rest time, that is, the time programmed to prevent a capacitor bank from being turned on again right after it is turned off, which could damage the capacitor and would certainly decrease the life of the contactors (which connect the capacitors to the power grid).

In the same way, every time the power factor exceeds the programmed switch-off point, by switching off inductive loads that were being compensated, the controller deactivates one or more capacitor banks, until the power factor exceeds the programmed switch-off point.

Another important feature is the disconnection of the capacitor banks when the grid voltage reaches high values, avoiding overvoltages of long duration, or when the harmonic content of the current and voltage is too high, which can cause resonances in the installation and damage the capacitors.

Example of a power factor controller

The controllers ST8200C controllers have several features whose purpose is to protect your investment in capacitor banks. Among them is the rest time, that is, the time programmed to prevent a capacitor bank from being turned on again right after it is turned off, which could damage the capacitor and would certainly decrease the life of the contactors (which connect the capacitors to the power grid).

Electrical Wiring Diagrams

The following figures show the connection schemes of the ST8200C controllers.

ST8200C phase-neutral connections

ST8200C Power factor controller

ST8200C phase-to-phase connections

ST8200C Power factor controller

NOTE: The current transformer (CT) must be positioned immediately after the power source (substation, transformer or switchboard) to measure the current coming from the loads and capacitor cells. Avoid having the CT signal wiring pass through the same conduits as the contactor control. Power is supplied via the auxiliary input.

ST8200C connections with user interface connection

ST8200C Power factor controller

Important notes on power factor controller installation

  • The current transformer (CT) must be positioned just after the power source (substation, transformer or switchboard) to measure the current coming from the loads and capacitor cells, and its wiring diameter must not be less than 2.5 mm2.
  • When the voltage measurement connection is between two phases, these must be different from the phase where you are monitoring the current through the CT. In turn, the TC should be connected to the controller’s TC1 and TC2 inputs.
  • When the voltage measurement connection is between phase and neutral, the CT should be on the phase used and connected to the controller’s TC1 and TC2 inputs.
  • Each contactor drive must be protected with an individual fuse.
  • The voltage and current measurement wiring (CT) must be in conduits separated from the contactor control by a distance of at least 10 cm. The wiring should also not pass through the power cable ducts, where the current from the capacitors will flow.
  • A specific CT must be placed for current measurement (always in the xxx/5A transformation ratio). If a measuring instrument already exists, the current measurement can take advantage of the instrument’s CT, provided that the CT signal is always connected in series with the controller. The CT terminals can be grounded.
  • Be careful about the supply voltage and the way the contactors are connected. The common wire of the contactors must be different from the one used for powering the controller. Remember that the maximum voltage/current for each drive output is 250VAC/5A.
  • When the optional REP interface is used, without connection to CTs and grid voltage, the electrical measurements of these two parameters will be reset to zero.
  • Voltage must be applied to the measurement input for both the voltage and the current parameters to be displayed in the electrical measurements menu. Otherwise, these two parameters will be reset to zero.

Power factor controller front panel

ST8200C Power factor controller

LEDs 1 to 16 indicate when the respective capacitor bank is being driven.

LED indicators

  • OK Equipment on
  • ST Lit, indicates an active alarm
  • RX Indicates serial channel receiving data
  • TX Indicates serial channel transmitting data

Theoretical foundations

Active Power

Active power, also known as real or useful power, is the power that performs useful work on a given load. This load, in turn, can be lighting or any other device that converts electrical energy into some other form of useful energy. This means that the active power is responsible for generating light, motion, heat, etc. The unit of measurement of active power is Watt (W). Depending on the situation, this could be the Kilowatt (kW).

Reactive power

Apparent power refers to the total power that a given source is capable of providing to a system. This consists of the vectorial sum of the active power and the reactive power. Its unit of measurement is the Volt Ampere (VA) or kilo Volt Ampere (kVA). In the context of electricity trading, the apparent power is all the power made available by the energy supplier to a given property.

Apparent power

Apparent power is defined as the total power that a given source is capable of providing. Its unit of measurement is the Volt Ampere (VA). In this sense, the relationship between apparent power and active power is called power factor. That is, it establishes the relationship between the amount of energy supplied by the source and the amount of energy that is actually transformed into work. When a power factor is high it means that a large part of the energy coming into the installation is transformed into work. When it is low it means that only a small portion of the energy received is converted into work. This means that the greater the amount of active power, the higher the power factor.

The power factor

The power factor represents the ratio of apparent power to active power. This means that the power factor represents the relationship between the amount of energy that was delivered by the source and the amount of energy that was actually transformed into work, that is, that was used in the property in question. On a scale of zero to one, the higher the power factor of a load, the greater its active power, that is, the power converted into work. Conversely, the lower a power factor is, the lower its active power and therefore the higher its reactive power (that which does no effective work).

Power factor correction

The objective of power factor correction is to gain efficiency, besides avoiding mismatches between voltage and current, not allowing equipment to operate with maladjusted loads and without effective production.

It is known that low power factor occurs when too much reactive power is consumed in relation to active power. The reactive power can be neutralized by a capacitive load, so the safest way to effectively correct the power factor and compensate for existing inductive loads is to install a capacitor bank.

In some cases, such as in very capacitive systems like transmission lines, an inductor bank is used to compensate for the capacitive effect.

Inductive loads produce a forward current in relation to the voltage. Capacitive loads produce a delay of the current with respect to the voltage. The capacitor bank and the inductor bank act by compensating the lag between the voltage and the current, basically “opposing” the inductive loads.

Causes of low power factor

Often the condition and maintenance of equipment can lead to a low power factor. Taking industry as an example, a series of precautions must be taken, in addition to considering situations that can be identified and corrected.

Take a look at some of the factors that are the major causes of low power factor in enterprises!

  • Low power motors acting together
  • Equipment working without load
  • Energy oversizing
  • Defective or very old equipment
  • Lighting using ballasts for lamps
  • Use of welding machines
  • Heat treatment apparatus

That is why it is important that the power factor stays within limits, considering the existing inductive load values. Thus, the proper sizing of the capacitor bank is necessary to have the best use of electrical energy.

Correcting the power factor in companies brings several advantages, see some of them in the list below.

  • Reduction of electric energy consumption
  • Increased useful life of facilities and equipment
  • Reduction of heat generated in equipment
  • Reduction of reactive current
  • Avoid unnecessary maintenance on equipment
  • No need to change conductor sections for larger gauge ones
  • No need to change the transformer for a higher capacity one

REFERENCE

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The use of Demand Controllers in the installations served by electric energy supply contracts by the concessionary is a way to guarantee that the system does not exceed the contractual limits, resulting in the application of fines. Small consumers are charged only for the energy used (consumption). Medium and large consumers pay for both the energy and the power made available.

The power appears in the bills of these consumers under the name of demand, which, in fact, corresponds to the average power verified in 15-minute intervals. The National Electrical Energy Agency (ANEEL) is the one that regulates and establishes these parameters in electric energy bills.

But do you know what a Demand Side Controller is and why using this equipment can help your company or industry to be more energy efficient?

What is the Demand Tracker?

ST8500C Demand ControllerThe purpose of a Demand Controller is to automatically manage the entrance and exit of loads on the electrical network, in order to prevent consumption exceeding the contracted demand, thus avoiding the payment of fines for excess demand.

The operation of a Power Demand Controller is very easy. The user registers the power value that he has contracted with the concessionaire, and the value of each load that must be managed, that is, turned on and off as needed. From that moment on, the equipment checks from time to time the power consumed in the busbar. Thus, it will turn on and off the loads that are registered so that the power consumed in the busbar is always below the measurement contracted by the concessionary.

The load connection is managed by load line or by schedule, and the demand schedule can be defined on a month-to-month basis. With the

ST8500C

from Alfacomp, for example, you can issue demand control reports via software. In addition, the log memory of this equipment is 60 days and the programming can be done via panel, supervisory, or APP.

Why do demand control in an industry

Doing demand control is indicated because, besides the management of the loads by demand, it allows the management of the loads by schedule. This allows, for example, a genset to be started during peak hours by connecting to a scheduled output per schedule.

A demand controller can also be useful in photovoltaic installations to prevent the injection of excess power into the utility grid. Alfacomp’s supervisory software ensures a history of the installation, giving the manager a tool to analyze its use and consumption of electricity.

The electricity bill for medium and large consumers is made up of the sum of consumption, demand, and overages. The consumption portion is calculated by multiplying the measured consumption by the consumption rate. The demand share, on the other hand, is calculated by multiplying the demand tariff by the contracted demand or by the measured demand (whichever is greater).

The

ST8500C Controllers

controllers have specific features to protect machinery and equipment. Among these is the rest time, which is the time programmed to prevent a load from being turned on again right after it is turned off – which can damage the machine and shorten the life of the contactors (which connect the loads to the electrical grid). The Controllers also allow programming the activation and shutdown of the loads with reverse logic, i.e., shutting down the Controller’s output for active loads, avoiding shutdowns due to control failure.

The demand controller and energy efficiency

The use of demand controls is not restricted to avoiding the fine for breach of contract. It is also interesting as a way of limiting consumption and consequently contingent electricity costs. That is why it is a device to implement energy-efficient industrial operation.

The use of this demand control equipment can bring the benefits of energy management to the consumer, reducing losses and in many cases allowing a reduction in the amount of the energy bill. From the supply point of view, the existence of Demand Side Control in consumer units allows better planning and better use of the distribution system, minimizing investments and increasing the energy efficiency of the sector.

energy efficiency

of the sector.

Pricing

The following are concepts and definitions involved in the pricing system:

  • Power: is the consumption capacity of electrical equipment, expressed in Watts (W) or kilowatts (kW).
  • Energy: is the amount of electricity used by an electrical appliance when it is left on for a given time. Its most usual units are kilowatt-hours (kWh) or megawatt-hours (Mwh).

The electricity tariff is the composition of calculated values that represent each portion of the investments and technical operations carried out by the agents of the production chain and the necessary structure so that the energy can be used by the consumer. The tariff represents, therefore, the sum of all the components of the industrial process of generation, transport (transmission and distribution), and commercialization of electric energy. In addition, there are charges to fund the application of public policies. The taxes and charges are listed on the electricity bill.

The concession companies supply electric energy to their consumers, based on obligations and rights established in a concession contract, entered into with the Federal Government, for the exploration of the public service of electric energy distribution in its concession area. At the time of signing the contract, the concessionaire recognizes that the current tariff level, i.e. the tariffs defined in the company’s tariff structure, together with the tariff adjustment and revision mechanisms established in that contract, are sufficient for the maintenance of its economic-financial balance (ANEEL, 2019).

Pricing methods refer to the way that consumers are classified in order to be charged for their electricity consumption. For the same, one should observe the tariff structure and consumer groups (PROCEL, 2011).

Tariff Structure

The tariff structure is a set of tariffs (price list) applicable to the electric power consumption and/or power demand components, according to the supply modality. It seeks to reflect the differences in costs related to the supply of energy to each type of consumer. From then on, the relativity of prices is defined. The structure comprises the differentiation of tariffs, according to consumption and demand components, supply voltage level, consumption class, season, period of the day, consumer location, etc. (BITU; BORN, 1993).

Electricity tariffs do not have the same value for all consumers. They are differentiated among tariff groups, according to the supply voltage, the moment of consumption, the type of tariff, and the consumer class. They can be structured and differentiated in many ways (VIEIRA, 2016).

Theoretically, a tariff could be defined for each consumer, but difficulties of various natures, such as, for example, the restrictions of commercialization, measurement system and collection, limit the degree of improvement of the tariff structure.

The consumer pays a final price that includes, in addition to the rates, fees or charges, contributions and taxes that are taxes, i.e., mandatory payments that do not represent a punishment for wrongdoing and must be provided by law (FUGIMOTO, 2010).

The fees or charges are independent of the amount of energy consumed and are related to the costs of servicing the consumption units. They are related to the costs associated with serving consumers, directly at the consumption units.

There are special rates such as those related to the additional fuel consumption in thermal power plants. The fees allow unforeseen increases in costs to be passed on to the consumer quickly. The final supply price paid by the customer is the composition of the tariff, contributions, fees, with taxes such as ICMS (FUGIMOTO, 2010).

Consumer Classification

For billing purposes, the consumer units are grouped into two tariff groups, defined mainly in function of the supply voltage and also, as a consequence, in function of the demand. If the utility supplies power at a voltage below 2300 Volts, the consumer is classified as being from “Group B” (low voltage); if the supply voltage is greater than or equal to 2300 Volts, the consumer is from “Group A” (high voltage). These groups were defined thus:

Group A Consumers

Group consisting of consumer units supplied at a voltage equal to or above 2.3 kV, or, also, supplied at a voltage below 2.3 kV from an underground distribution system and billed in this Group, on an optional basis, as defined in ANEEL Resolution 456, characterized by the binomial tariff structure and subdivided into subgroups A1, A2, A3, A3a, A4 and AS. The table below presents these subgroups.

Subgroups

Tension

A1 Supply voltage equal or higher than 230 kV
A2 Supply voltage from 88 kV to 138 kV
A3 Supply voltage 69 kV
A3a Supply voltage from 30 kV to 44 kV
A4 Supply voltage from 2.3 kV to 25 kV
AS Supply voltage below 2.3 kV served from an underground distribution system and included in this Group on an optional basis.

Consumers in this group are charged for both the demand and the energy they consume. These consumers can fall into one of two tariff alternatives:
– Conventional pricing;
– Hourly-seasonal pricing.

Conventional Pricing

The framing of the conventional tariff requires a specific contract with the concessionaire in which a single value of demand intended by the consumer (contracted demand) is agreed upon, regardless of the time of day (peak or off-peak) or the period of the year (dry or wet).

Consumers in Group A, subgroups A3a, A4 or AS, may be included in the conventional tariff when the contracted demand is less than 300 kW, as long as there have not been, in the previous 11 months, 3 (three) consecutive records or 6 (six) alternate records of demand over 300 kW.

The electric energy bill for these consumers is composed of the sum of consumption, demand, and overages. The consumption portion is calculated by multiplying the measured consumption by the consumption rate.

The demand share is calculated by multiplying the demand tariff by the contracted demand or by the measured demand (the higher of the two), if it does not exceed the contracted demand by 10%.

The overage portion is charged only when the measured demand exceeds the contracted demand by more than 10%. It is calculated by multiplying the overage tariff by the value of the measured demand that exceeds the contracted demand (BRASIL, 2000).

Horo-Seasonal Pricing

This modality is characterized by the application of differentiated tariffs for electric power consumption and power demand according to the hours of use of the day and the periods of the year.

The hour-seasonal charging structure can be applied according to the following charging models:

a) Green Rate

The Green tariff for Group A consumers. This tariff mode requires a specific contract with the concessionaire in which the demand desired by the consumer (contracted demand) is agreed, regardless of the time of day (peak or off-peak). Although not explicit, Aneel’s Resolution 414 of 2010 allows two different demand values to be contracted, one for the dry period and another for the wet period (BRASIL, 2010). The electric energy bill for these consumers is composed of the sum of consumption (on- and off-peak), demand, and overages.

The demand share is calculated by multiplying the demand tariff by the contracted demand or by the measured demand (the higher of the two) if it does not exceed the contracted demand by more than 10%. The demand charge is unique, regardless of the time of day or period of the year.
The overage portion is charged only when the measured demand exceeds the contracted demand by more than 10%. It is calculated by multiplying the overage tariff by the value of the measured demand that exceeds the contracted demand.

b) Horo-seasonal Blue Fare

The inclusion of Group A consumers in the hourly blue tariff is mandatory for consumers of subgroups A1, A2 or A3. This tariff modality requires a specific contract with the concessionaire in which both the value of the demand intended by the consumer during peak hours (peak contracted demand) and the value intended during off-peak hours (off-peak contracted demand) are agreed upon.

Although not explicit, as with the green tariff, Resolution 414 allows different values to be contracted for the dry period and the wet period (BRASIL, 2010).

The electric energy bill for these consumers is composed of the sum of the parts referring to consumption and demand and, if any, overages. In all plots the differentiation between peak and off-peak hours is observed (CENTRAIS ELÉTRICAS BRASILEIRAS, 2011).

The demand portion is calculated by adding the product of the on-peak demand charge and the on-peak contracted demand (or the on-peak metered demand, subject to overshoot tolerances) to the product of the off-peak demand charge and the off-peak contracted demand (or the off-peak metered demand, subject to overshoot tolerances).

The demand charges are not differentiated by period of the year. The overage portion is charged only when the measured demand exceeds the contracted demand above the tolerance limits of 5% for the A1, A2 and A3 sub-groups and 10% for the other sub-groups. The value of this portion is obtained by multiplying the overage charge by the value of the metered demand that exceeds the contracted demand (PROCEL, 2011).

Group B Consumers

Consumer units served at voltage below 2.3 kV, or even units served at voltage above 2.3 kV and billed in this group, are characterized by the monomial tariff structure (ANEEL, 2000).

A group B consumer is one who receives electricity at a voltage between 220 and 380 V and has an adhesion contract with the energy concessionaire. Adhesion contract is a contractual instrument, with clauses bound to the norms and regulations approved by ANEEL, the content of which cannot be modified by the concessionaire or consumer, to be accepted or rejected in full (ANEEL, 2000).

Group B consumers (low voltage< 2,300 Volts) are classified as:

  • B1 – residential;
  • B2 – rural;
  • B3 – other classes;
  • B4 – public lighting.

Low voltage consumers (Group B) are further classified according to the number of phases. There are three types of supply, depending on the number of phases:

  • Type A – single-phase – two conductors (one phase and neutral);
  • Type B – two-phase – three conductors (two phases and neutral);
  • Type C – three-phase – four conductors (three phases and neutral).

To determine these, the installed load of each consumer unit must be calculated. This load will be the sum of the rated plate powers of the electrical appliances and the declared lighting powers. When there are motor loads, their respective quantities and individual powers should be computed (PROCEL,2011).

In Group B consumers, only energy consumption is billed, and there is no charge for power demand (PROCEL, 2011).

Off-peak and Peak Times

Peak time (P) is the period defined by the distributor and composed of three consecutive daily hours, except for Saturdays, Sundays, Carnival Tuesday, Passion Friday, Corpus Christi, and eight holiday days as described in ANEEL Resolution 414, considering the load curve of its electrical system, approved by ANEEL for the entire concession area. The off-peak hour (F) is the period composed of the set of consecutive and complementary daily hours to those defined in the peak hour (VIANA; BORTONI; NOGUEIRA, 2012).

Peak and Off-Peak times for a consumer unit

Demand ControlSource: Viana, Bortoni, and Nogueira (2012).

Also according to Viana, Bortoni, and Nogueira (2012), these schedules are defined by the concessionaire due mainly to its supply capacity. The typical power supply curve of a utility can be seen through the figure below, where the highest demand value usually occurs during peak hours.

Typical power supply curve of a utility

Demand Control

Source: Viana, Bortoni, and Nogueira (2012).

Dry and Wet Periods

These periods are normally directly related to the periods where the flood variations of the water reservoirs used for power generation occur. The Dry Period corresponds to the period of 07 (seven) consecutive billing cycles, starting in May and ending in November of each year; it is, generally, the period with little rain. The Wet period corresponds to the period of 05 (five) consecutive billing cycles, comprising the supplies covered by the readings from December of one year to April of the following year; it is generally the period with more rainfall (CARVALHO, 2011).

Electricity demand

According to ANEEL’s Resolution 456 in Art. 2º, § VIII, demand is the average of the active or reactive electric powers requested to the electric system by the installed load portion in operation at the consumer unit, during a specified time interval. Thus, this average power, expressed in kilowatts (kW) and kilovolt-ampere-reactive (kvar), respectively. It can be calculated, for example, by dividing the electrical energy absorbed by the load in a certain time interval Δt, by this time interval Δt, and can be expressed by the equation below.

Demand Control

In Brazil the time interval (integration period) is 15 minutes, so in one month we will have: 30 days x 24 hours / 15 minutes = 2880 intervals (ANEEL, 2019).

According to Suppa and Terada (2010), we have synchronous and asynchronous measurement methods. The synchronous measurement method is the one used by all Brazilian utilities and by most countries, measuring active power in a certain time interval that can vary from 15 to 60 minutes in most cases.

In practice, what is done is to integrate the energy pulses within this interval, therefore called integration interval, obtaining what we call active energy demand, that is, the demand is the average energy consumed in each 15-minute interval not fully existing before the interval closes.

Generally, the utility bills for the highest values registered in the off-peak and peak periods or for the contracted values, whichever are higher. At each start of the integration interval the consumption is reset to zero, starting a new countdown. If at the end of the interval the average closing value exceeds the allowed limit, the user will face heavy fines for exceeding the limit.

Also according to the resolution, some definitions are adopted between the distributor and the consumer through a service provision contract, and they are (ANEEL, 2019):

  • Demand: average of the active or reactive electric power demanded from the electric system by the installed load portion in operation at the consumer unit, during a specified time interval.
  • Contracted demand: active power demand to be compulsorily and continuously made available by the concessionaire, at the point of delivery, according to the value and period of validity established in the supply contract and which must be fully paid for, whether it is used or not during the billing period, expressed in kilowatts (kW);
  • Exceeding demand: portion of the measured demand that exceeds the value of the contracted demand, expressed in kilowatts (kW);
  • Measured demand: highest active power demand verified by measurement, integralized in an interval of 15 (fifteen) minutes expressed in kilowatts (kW);
  • Billable demand: active power demand value identified according to the criteria established and considered for billing purposes, with the application of the respective tariff, expressed in kilowatts (kW).

For consumption billing, the total kWh consumed during the period is accumulated: off dry peak or off wet peak, and dry peak or wet peak. For each of these periods, a differentiated consumption tariff applies, and the total is the consumption billing portion. Evidently, consumption tariffs in dry periods are higher than in wet periods, and during peak hours is more expensive than during off-peak hours (PROCEL, 2011).

The charge is always a function of contracted demand and consumption. When you contract a demand, you are actually requesting that the supplying company makes a certain amount of energy available to be consumed. In this way, three cases of charging may occur (PROCEL, 2011):

  • Registered demand lower than the contracted demand: the consumption and demand tariff corresponding to the contracted value applies;
  • Registered demand higher than the contracted demand, but within the overrun tolerance: the consumption and demand tariff corresponding to the demand applies
  • Registered demand higher than the contracted demand and above the tolerance: the consumption and demand tariff corresponding to the contracted demand is applied, and to this is added the application of the overage tariff, corresponding to the difference between the registered demand and the contracted demand. In other words, you pay the normal charge for the contracted service, and an overage charge on all the excess.

Demand Exceedance

According to Aneel (2018), energy demand is contracted with the utility (you pay for it regardless of usage). The demand monitoring is done by the average of the 15 minutes of integration. Its measurement is based on the “average” of the 15 minutes of demand integration. The exceeding of the electric demand is controlled based on the average values of the 15 minutes integration, that is, the average demand of 15 minutes cannot exceed the contracted demand. If the overrun occurs, the concessionary will charge the fine based on the highest recorded value. According to the type of consumer, there is a tolerance on the contracted demand value so that no fines are charged, as defined in Resolution 456 of November 29, 2000, Art. 2, § VIII:

  • 5%, for units with a supply voltage greater than or equal to 69 kV (blue tariff);
  • 10%, for units whose supply voltage is lower than 69 kV and in the billing month, the off-peak demand (blue tariff) and the demand (green tariff), are higher than 100 kW;
  • 20%, for units served at a voltage of less than 69 kV, and in the billing month, off-peak demand (blue tariff) and demand (green tariff) from 50 to 100 kW.

Demand Control

According to F.S Ozur (2011), The demand controller is an electronic equipment whose main function is to maintain the active power demand of a consumer unit, within predetermined limit values, acting, if necessary, on some part of the Demand Controllers also controls the power factor and energy consumption. Controlling the demand is fundamental, not only for the consumer to reduce his costs with electric energy, but also for the concessionaire that needs to operate in a well-dimensioned way, avoiding interruptions or poor supply quality.

Example of a demand controller

The ST8500C demand controllers were developed by Alfacomp to, through continuous monitoring and proper load management, keep the electrical power within pre-set limits.

Programming and operating the equipment is very simple, because it is compatible with other important tools, such as standard energy meter interfaces, according to the ABNT NBR14522 standard.

In addition, the ST8500C measures and records various electrical quantities (memory for 30 days of records), providing the user with a complete examination of your facility’s power system. It is also possible to use the equipment in conjunction with the ST-Conecta software (software that comes with the product), which allows maximizing the data analysis and management.

More than just power demand controllers, the ST8500C devices are powerful electric power management systems.

Principle of operation

The ST8500C controllers receive continuous load power information through the serial user interface, opto-coupled, standardized through the NBR14.522 (ABNT) standard, available in power electronic meters. The information, in the model with CT’s, can be passed on via the electrical bus connection, with the use of current transformers (CT X/5) and voltage signals. The electrical energy demand of the load is calculated using mathematical algorithms.

As needed, that is, whenever the projected demand is above the set-point, the ST8500C controllers deactivate one or more loads, promoting their correction. In the same way, every time the projected demand falls below the stipulated level, the controller activates one or more loads.

The ST8500C controllers have several features aimed at protecting your machines and equipment. Among these is the rest time, which is the time programmed to prevent a load from being turned on again right after it is turned off – which can damage the machine and shorten the life of the contactors (which connect the loads to the electrical grid). The controllers also allow you to program the activation and shutdown of the loads with reverse logic, i.e., shutting down the controller output for active loads, avoiding downtime due to control failure.

Visual inspection

Before installation, make a careful visual inspection to make sure that the product has not been damaged in transit.

Electrical Wiring Diagrams

The following figures show the connection schemes of the ST8500C controllers.

1. model with CT input

ST8500C Demand Controller

2. Model with opto-coupled input

ST8500C Demand Controller

Drive Connections

ST8500C Demand Controller

Important notes on equipment installation

  • In the model with current transformers (CTs), the transformation ratio should be X/5A.
  • Each contactor drive must be protected with an individual fuse.
  • The wiring that measures voltage should be placed in separate conduits from the contactor control with a distance of at least 10 cm.
    The wiring should also not pass through the power cable ducts, where the load current will circulate.
  • Be careful about the supply voltage and the way the contactors are connected. The common wire of the contactors must be different from the one used
    on the controller’s power supply. Remember that the maximum voltage/current for each drive output is 250VAC/5A.
  • The maximum supply voltage of the controller, which is used for the equipment to work, is 270VAC, while the measurement voltage,
    used for calculations for display information, can go up to 600VAC.
  • In the opto-coupled model it is necessary to apply voltage to the measurement input in order to display them in the electrical measurements menu,
    both the voltage parameter and the current parameter. Otherwise, these two parameters will be reset to zero.

Attention!

The ST8500C’s voltage supply can be from any source, as long as it stays within the range of 80 to 270 VAC.

Demand controller front panel

ST8500C Demand Controller

NOTE: The ST8500C display backlighting is only activated when a key is pressed. If no key is pressed within 3 minutes, the lighting will turn off automatically.

LED indicators

  • OK Equipment on
  • ST Lit, indicates an active alarm
  • RX Indicates serial channel receiving data
  • TX Indicates serial channel transmitting data

REFERENCE

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Se você busca uma forma de reduzir o espaço ocupado pelos relés no painel de automação, apresentamos aqui uma solução simples, funcional e de excelente custo-benefício. Veja o esquemático abaixo.ID2908 – Isolador a relé para 8 saídas digitais
EsID2908 – Isolador a relé para 8 saídas digitaiste dispositivo foi projetado para criar 8 saídas a relé isoladas para utilização com CLPs de saída a transistor em 24 VCC. A montagem vertical do módulo isolador permite termos 8 relés em apenas 23 mm do trilho DIN.

Componentes:

  • Diodos D9 a D16: 1N4148
  • Relés K1 a K8: DSY2Y-S-224L
  • LEDs D1 a D8: LED 3mm vermelho
  • Conector J1: STLZ1550/9-3.18H
  • Conectores J2 e J3:  STLZ 1550/8-3.18H

Na busca constante por competitividade e redução de custos, a indústria de componentes eletro-eletrônicos procura oferecer dispositivos cada dia mais compactos, viabilizando assim montagens de quadros de comando menores e mais econômicos. Boa parte da área de um painel elétrico com muitas saídas digitais é destinada aos relés. Pois bem, imagine reduzir pela metade o espaço ocupado pelos relés no quadro de comando. Considerando relés medindo 6 mm de largura, por  exemplo, 64 relés enfileirados irão ocupar 38,4 cm. Com o ID2908, 64 relés ocupam apenas 18,4 cm.

O módulo ID2908 constitui um isolador a relé para 8 saídas digitais de 24V. As bobinas dos relés tem uma ligação em comum no borne 0V. O módulo possui 8 saídas independentes e isoladas; S0 até S7. Ocupando apenas 23 mm no trilho DIN, o módulo funciona como borneira, simplificando a montagem de quadros de comando e economizando espaço. 8 LEDs indicam o estado dos relés. As conexões são por bornes destacáveis, facilitando a troca rápida de módulos.

Especificações técnicas

Tensão de acionamento 24 VCC
Capacidade de comutação 2A em 220 VCA
Indicação 8 LEDs indicam o estado dos relés
Dimensões Altura 88 x Largura 23 x Profundidade 74 mm (conectores incluídos)
Formato Placa eletrônica em suporte metálico aberto e fixação para trilho DIN

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Electromagnetic flow meters use Faraday’s Law to detect and measure flow. Inside an electromagnetic flow transmitter there is a coil that generates a magnetic field and electrodes that capture the electric field resulting from the movement of the liquid that is under the magnetic field.
According to Faraday’s Law, moving conductive liquids within a magnetic field generates an electromotive force (voltage). In other words, the flow velocity of the liquid moving within the magnetic field generates a proportional electric field. The electric field E is proportional to V x B x D (velocity x magnetic field x diameter).


Electromagnetic flow transmitters have the following characteristics:

  • They are not affected by temperature, pressure, density, or viscosity of the liquid;
  • They also detect the flow in liquids contaminated with solids and bubbles;
  • They do not cause pressure loss;
  • They use no moving parts and are therefore more reliable;

They cannot be used in liquids that are not conductive.
Conductivity expresses the ease with which the liquid allows electric current to conduct. Conductivity is measured in S/cm (siemens per centimeter). Ordinary tap water has an average conductivity of 100 to 200 μS/cm, mineral water 500 μS/cm or more, and pure water 0.1 μS/cm or less.

The electromagnetic flow transmitter TVE20 allows the flow measurement of liquids in pipes from 10 to 350 millimeters in diameter using the electromagnetic principle based on Faraday’s law.

Main Features

  • Multi-electrode structure;
  • High accuracy;
  • No moving parts;
  • Wide measurement range;
  • Power supply: 85 to 265 VAC or 18 to 36 VDC;
  • It does not obstruct the flow of the measured liquid;
  • Several flange options;
  • Several options of operating frequencies;
  • It allows you to detect the direction of the liquid;
  • Surge resistant electronics;

Applications

  • Water and sewage;
  • Chemical industry;
  • Food industry;
  • Agriculture;
  • Effluent treatment.

Technical specifications of the TVE20 flow transmitter

  • Size: DN10 to DN350
  • Medium: Conductive liquids
  • Media temperature: Class E∠60°C Grade CH∠180°C
  • Accuracy: 0.25% to 0.5%.
  • Repeatability: 0.1% to 0.17
  • Pipe Pressure: 0.6, 1.0, 1.6, 2.5, 4.0, 6.4 MPa (or customer specified)
  • Display indications: Instantaneous flow rate, totalization, speed, flow rate
  • Output signals: 4 to 20mA, pulses, RS485, Hart
  • Power supply: 85 to 265 VAC or 18 to 36 VDC
  • Converter Type: Integrative
  • Protection: IP65/IP68
  • Explosion proof: Ex deibmb IIC T3 ~ 6
  • Speed: 0.05 to 12 m/s
  • Coating: PU (DN25 to DN500) / F4 (PTFE) (DN25 to DN1600) / F46 (FEP) (DN10 to DN200) / PFA (DN10 to 30)
  • Direction of flow: Direct and reverse
  • Electrode material: 316L, Pt, Ta, Ti, HB, HC, WC
  • Number of electrodes: 3 to 6 units
  • Flange material: SS/CS
  • Alarm (normally open): Empty, excitation, upper and lower limit
  • Ambient temperature: -30°C to 60°C
  • Communication protocol: Modbus, Hart

Measuring ranges (m3/h)

DN (mm)

Measuring Range

Accuracy

DN (mm)

Measuring Range

Accuracy

DN10 0,014 a 3,39 0,08 a 2,82 DN300 12,7 a 3052 76 a 2543
DN15 0,03 a 7,63 0,19 a 6,35 DN350 17,3 a 4154 103 a 3461
DN20 0,06 a 13,56 0,33 a 11,34 DN400 22,6 a 5425 1355 a 4521
DN25 0,09 a 21,19 0,52 a 17,66 DN450 28,6 a 6867 171 a 5722
DN32 0,14 a 34,72 0,86 a 29,93 DN500 35,3 a 8478 211 a 7065
DN40 0,23 a 54,25 1,35 a 45,21 DN600 51 a 12208 305 a 10173
DN50 0,35 a 84,78 2,12 a 70,65 DN700 69 a 16616 415 a 13847
DN65 0,6 a 143 3,58 a 119 DN800 90 a 21703 542 a 18086
DN80 0,90 a 217 5,43 a 180 DN900 114 a 27468 686 a 22890
DN100 1,41 a 339 8,48 a 282 DN1000 141 s 33912 847 a 28260
DN125 2,21 a 529 13,25 a 441 DN1200 203 a 48833 1221 a 40694
DN150 3,18 a 763 19,08 a 635 DN1400 277 a 66467 1662 a 55389
DN200 5,65 a 1356 33,91 a 1130 DN1600 361 a 86814 2171 a 72345
DN250 8,83 a 2119 52,99 a 1766 DN1800 457 a 109874 2747 a 91562

Electromagnetic flow transmitter TVE20 dimensions (mm)

DN

H

L

D1

D

n-fd1

C

Pressure

10 160 260 60 90 4-f14 14 PN4.0
15 265 65 95 4-f14 14
20 272 75 105 4-f14 16
25 280 85 115 4-f14 16
32 290 100 140 4-f18 18
40 200 305 110 150 4-f18 18
50 320 125 165 4-f18 20
65 335 145 185 4-f18 20 PN1.6
80 350 160 200 8-f18 20
100 250 370 180 220 8-f18 22
125 405 210 250 8-f18 22
150 300 435 240 285 8-f22 24
200 350 495 295 340 12-f22 24
250 400 545 350 395 12-f22 26 PN1.0
300 500 595 400 445 12-f22 26
350 630 460 505 16-f22 26
400 600 685 515 565 16-f26 26
450 735 565 615 20-f26 28
500 790 620 670 20-f26 28
600 900 725 780 20-f30 34
700 700 1035 840 895 24-f30 30
800 800 1140 950 1015 24-f33 32
900 900 1245 1050 1115 28-f33 34
1000 1000 135 1160 1230 28-f36 34
25 160 280 100 140 4-f18 24 PN6.4
32 290 110 155 4-f22 24
40 200 305 125 170 4-f22 26
50 320 135 180 4-f22 26
65 340 160 205 8-f22 26
80 350 170 215 8-f22 28
100 250 375 200 250 8-f26 30
125 415 240 295 8-f30 34
150 300 485 280 345 8-f30 36
200 350 520 345 415 12-f36 42
250 400 570 400 470 12-f36 46
300 500 625 460 530 16-f36 52
350 680 525 600 16-f39 56

How to select the electrode material

Electrode

Application

Not suitable for

316L Domestic water, industrial water, raw water, domestic sewage, light acids, light alkalis, salt water. Strong acids, strong alkalis.
Hastelloy alloy B Non-oxidizing acids with concentration less than 10%, Sodium hydroxide with concentration less than 50%, ammonium hydroxide, phosphoric acid, organic acids. Nitric acid.
Hastelloy C Compound acids (such as chromic acid solutions and sulfuric acid), oxidizing salts (such as sea water, including CU+++, Fe+++). Hydrochloric acid.
Titanium Salts (such as sodium and potassium chlorides, ammonium salts, sodium hypochlorite), potassium hydroxide < 50%, ammonium hydroxide, barium hydroxide, alkaline solutions. Hydrochloric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, and other reducing acids.
Tantalum Hydrochloric acid < 40%, sulfuric acid, chlorine dioxide, iron chloride, hypochloric acids, sodium chloride, lead acetate, nitric acid. Alkaline solutions, hydrofluoric acid.
Platinum gold Virtually all alkaline solutions. Aqua regia, ammonium salt.

How to select the lining material

Select according to liquid and temperature.

Coating

Symbol

Performance

Temperature

Application

Rubber CR Resistance to high concentrations of acid and basic salts. ≤70oC Domestic and industrial water, seawater.
PTFE PTFE Stable and resistant to boiling liquids, acids, aqua regia, and concentrated alkalis. ≤150oC Corrosive acids, saline solutions.
Fluorinated ethylene propylene F46 or FEP Chemical properties equivalent to F4, tensile strength superior to F4. ≤180oC Corrosive and saline solutions, negative pressures.
Polyurethane PU High wear resistance, not suitable for acids. ≤70oC Sludge, slurries and other abrasives.

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Do you know how the PLC’s 4 to 20 mA analog inputs work and why they are so sensitive?

This article addresses this and proposes a simple solution to protect the 4 to 20 mA analog inputs of the PLC.

How the PLC’s 4 to 20 mA analog inputs work

Most 4 to 20 mA inputs in CLPs have a resistor of about 150 to 200 ohms at their input. See below for a typical circuit.SS2701 - Analog input surge protector

In the example in the picture above, we show a hydrostatic level transmitter.

This type of sensor is widely used to measure the water level in reservoirs belonging to the municipal water supply system.

The hydrostatic level transmitter works submerged, and because it is in direct contact with water, it is a path for electrical surges that normally enter the network and seek ground.

When a hydrostatic level sensor burns out due to a surge, it often ceases to function as a 4 to 20 mA regulator and delivers the unrestricted 24 V at the output.

Whether it is a hydrostatic level transmitter, a pressure sensor, or any other field instrument that, instead of delivering a 4 to 20 mA current, delivers the 24 V of the supply directly to the analog input, this will damage the analog input by the excess voltage and current.

What happens when the sensor shorts out and supplies the 24 V, with no current limit, to the 4 to 20 mA analog input?

Let’s say that the analog input is provided with a 200 ohms resistor. The current over the resistor will be:

I = 24V / 200 ohms = 120 mA and the Power over the resistor P = 24 V x 120 mA = 2.88 W

The resistors used in the analog inputs of the CLP are not sized to withstand this power and fatally burn out.

Solution to protect the analog input against excess current

The solution is simple; we need a voltage limiter and a current limiter working together.

As a voltage limiter we use the TVS diode and as a current limiter we use the PTC thermistor.

SS2701 - Analog input surge protector

Using the solution presented, when the field sensor is shorted, and the 24 V from the source goes straight through, the TVS diode will conduct, limiting the voltage at the analog input to 6 V.

The current on the PTC thermistor trying to exceed 50 mA will cause the PTC to heat up and change its original resistance from about 2 ohms to a resistance that limits the current to 50 mA.

In the case of the circuit shown, the resistance of the PTC will change to about: R = (24 V – 6 V) / 50 mA = 360 ohms.

Over the 200 ohms resistor of the analog input the resulting voltage will be 6 V, and the current 30 mA, resulting in a maximum power of 180 mW, which is not enough to damage the component.

The thermistor works like a resettable fuse, because after the replacement of the damaged (shorted) sensor, and having ceased the excessive current, the PTC will cool down and return to having only 2 ohms of resistance.

The PTC selected is of a type specially designed for overcurrent protection. The Resettable Fuses – Multifuse® PPTC line from Bourns is an example of such components.

The TVS diode is a fast diode specially designed to absorb surge voltages and is widely used in SPD (Surge Protection Device) circuits.

Complete protective circuit for analog 4 to 20 mA PLC inputs

We now present a complete circuit of an SPD for the protection of 4 to 20 mA inputs.

SS2701 - Analog input surge protector

The circuit presented protects not only the analog channel, but also the 24 V supply that is provided to the field sensor.

The protection is in three stages, by means of the three types of surge suppressors:

  • Gas spark gap;
  • Metal oxide varistor;
  • TVS diode.

The inductors that separate each stage of the protection help to delay and dampen the surge.

SPD PCB for analog inputs 4 to 20 mA

SS2701 - Analog input surge protector

QTY DESCRIPTION

  • 4 CN1, CN2 – AKZ-700 – 2
  • 1 D1 – P6KE30A (TVS)
  • 1 D2 – P6KE6A (TVS)
  • 1 F1 – Resetable fuse (PTC) 50 mA
  • 1 F2 – 50 mA resettable fuse (PTC)
  • 4 L1, L2, L3, L4 – Inductor 100uH
  • 2 RV1, RV2 – S10K30 (Varistor)
  • 2 SA1, SA2 – 75V (spark gap)
  • 1 Spacer 15 mm
  • 1 RS75 Female Foot
  • 1 RS75 Male Foot
  • 1 SS2701 PCB

Request additional information or a quote for the Analog Input Protector

The module SS2702 module is an analog channel protector against electrical surges caused by over-voltages in the field wiring. Assembled in printed circuit board and housed in a plastic DIN-rail mount, the module incorporates five surge protection circuits, one to prevent surges from damaging the 24V power supply circuit and the other four for protecting analog channels. Each circuit is fitted with a fuse, gas spark gap, metal oxide varistor, suppressor diode, and inductors. The module replaces, with advantages in cost, space, and assembly time, an arrangement of four protectors, five fuses, and sixteen terminal blocks. One of the product’s differentials is the fact that it is the only one in the market equipped with resettable fuses (PTC).

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The 60 km radio link kit allows communicating RS232 and RS485 equipment up to 60 km when there is direct line of sight between the points. The kit gathers the necessary equipment and materials to establish serial communication between two points. The communication standard can be RS232 or RS485. The allowed serial speed is 1,200 to 230,400 bps. The range of the link is up to 60 km with sighting. Application example: communication between CLPs.

See below the composition of the radio link kit 60 km.


Composition of the 60 km radio link kit

Application example of the 60 km radio link kit

The following figure shows an example of the kit’s application. In the example, a computer running supervisory software supervises and controls a PLC up to 60 km away with direct line of sight.

Description of the P900 radio modem

The P900 radio modem with spread spectrum technology
spread spectrum
has connectors and LEDs that facilitate installation and use.

The rugged enclosure, wide operating temperature range, and low cost make the P900 radio modem the ideal solution for controlling and monitoring remote telemetry stations and for all kinds of industrial applications where serial communication is required.

The P900 also incorporates the ability to compose next-generation Mesh networks with the ability to automatically re-establish communication routes(Self Healing).

Features of the P900 radio modem

  • Allows up to 276 kbps
  • Low cost
  • Point to Point, Multipoint and Mesh
  • Mesh network with automatic forwarding
  • Store & Forward – the radio works as a repeater
  • Mesh configuration as master, repeater or terminal unit
  • Operating temperature (-55 C to +85 C)
  • Adjustable output power: 100mW-1W
  • Reduced dimensions
  • Low power consumption in sleep mode
  • Four-stage filter provides high rejection of noise and interference
  • Error correction (FEC), 32-bit CRC, and 128-bit AES

Applications of the P900 radio modem

  • Measuring utilities
  • Remote Unit Telemetry
  • Sensing electricity, oil and gas
  • Communication with digital signage panels
  • Serial communication in industrial environment

Certification

The P900 radio modem is Anatel certified.

Technical Specifications

  • Operating band: 902-928 MHz
  • Scattering method: Frequency jumps
  • Error detection algorithms: Hamming, BCH, Golay, Reed-Solomon
  • Error detection: 32-bit CRC, ARQ
  • Encryption: Optional (see -AES option)
  • Range: 60 km
  • Sensitivity:
    • -114 dBm at 57.6 kbps
    • -112 dBm at 115.2 kbps
    • -109 dBm at 172.8 kbps
    • -107 dBm at 230.4 kbps
  • Output power: 100 mW to 1 W (20 to 30 dBm)
  • Serial Interface: RS232/485 (Selectable)
  • Serial speed: up to 230.4 kbps asynchronous
  • RF communication speed: 57.6 to 276 kbps
  • Operation Modes: Mesh, Auto Routing, Store and For-ward, Self Healing, Packet Routing Modes
  • Interface: RxD1, TxD1, RTS, CTS DCD, DSR, DTR, RxD2, TxD2, RSSI LEDs, Tx/Rx LEDs, Reset, Config, Wake-up, RSmode, 4 digital inputs/outputs, 1 analog input, 1 analog output
  • Remote diagnostics: battery voltage, temperature, RSSI, packet statistics
  • Power supply: 9 to 30 VDC
  • Consumption:
    • Rx: 45 mA to 98 mA
    • Tx : 1000 mA to 1400 mA
  • Connectors:
    • Antenna: SMA female
    • Data: DB-9F
  • Operating temperature: -55 C – +85 C
  • Weight: 120 g
  • Dimensions: 46 mm x 66 mm x 25 mm

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Medidor de vazão ultrassônico – o que é?

O medidor de vazão ultrassônico mede a velocidade de um fluido com ultrassom para calcular a vazão do líquido. Ele calcula a diferença no tempo de trânsito medido entre os pulsos de ultrassom que se propagam na direção e contra a direção do fluxo ou medindo a mudança de frequência devida ao efeito Doppler.TDS-100H Medidor ultrassônico de vazão portátil

Medidor de vazão ultrassônico – como funciona?

O medidor ultrassônico de vazão é um tipo de medidor de vazão que mede a velocidade de um fluido com ultrassom para calcular a vazão do líquido. Usando transdutores ultrassônicos, o medidor de vazão pode medir a velocidade média ao longo do caminho de um feixe de ultrassom emitido, calculando a média da diferença no tempo de trânsito medido entre os pulsos de ultrassom que se propagam na direção e contra a direção do fluxo ou medindo a mudança de frequência devida ao efeito Doppler. Os medidores de vazão ultrassônicos são afetados pelas propriedades acústicas do fluido e podem ser afetados pela temperatura, densidade, viscosidade e partículas suspensas. Os medidores de vazão ultrassônicos apresentam ótima relação custo benefício pois não utilizam peças móveis, são fáceis de instalar, não demandam seccionar ou furar a tubulação, e são de fácil manutenção.

Tipos de medidores de vazão ultrassônicos

Existem três tipos diferentes de medidores de vazão ultrassônicos. Os medidores de vazão de transmissão por tempo de transito – intrusivo e clamp-on (não intrusivo). Os medidores de vazão ultrassônicos por efeito Doppler são chamados de medidores de vazão de reflexão ou Doppler. O terceiro tipo é o medidor de vazão de canal aberto.

Medidor de vazão ultrassônico por tempo de trânsito

Os medidores ultrassônicos de vazão medem o tempo de trânsito dos pulsos ultrassônicos que se propagam com e contra a direção do fluxo. Essa diferença de tempo é uma medida para a velocidade média do fluido ao longo do caminho do feixe ultrassônico. Usando os tempos de trânsito absolutos Tup e Tdown, tanto a velocidade média do fluido v quanto a velocidade do som c podem ser calculados. Usando esses dois tempos de trânsito, a distância entre os transdutores de recepção e transmissão L e o ângulo de inclinação α , se assumirmos que o som tem que ir contra o fluxo ao subir e ao longo do fluxo ao retornar para baixo, pode-se escrever as seguintes equações a partir da definição de velocidade:

TDS-100H Medidor ultrassônico de vazão portátil

Somando e subtraindo as equações acima obtemos,

TDS-100H Medidor ultrassônico de vazão portátil

onde v é a velocidade média do fluido ao longo do caminho do som e c é a velocidade do som.

Medidores de vazão ultrassônico por efeito Doppler

Outro método na medição de vazão ultrassônica é o uso do deslocamento Doppler que resulta da reflexão de um feixe ultrassônico em materiais refletivos, como partículas sólidas ou bolhas de ar aprisionadas em um fluido em fluxo, ou a turbulência do próprio fluido, se o líquido está limpo. Os medidores de vazão Doppler são usados ​​para lamas, líquidos com bolhas, gases com partículas refletoras de som.

Este tipo de medidor de vazão também pode ser usado para medir a taxa de fluxo sanguíneo, passando um feixe ultrassônico através dos tecidos, refletindo em uma placa, invertendo a direção do feixe e repetindo a medição, o volume do fluxo sanguíneo pode ser estimado. A frequência do feixe transmitido é afetada pelo movimento do sangue no vaso e, comparando a frequência do feixe a montante versus a jusante, permitindo a medição do fluxo de sangue através do vaso. A diferença entre as duas frequências é uma medida do fluxo de volume real. Um sensor de feixe largo também pode ser usado para medir o fluxo independente da área da seção transversal do vaso sanguíneo.

Medidores de vazão ultrassônico de canal aberto

Neste caso, o elemento ultrassônico está na verdade medindo a altura da água no canal aberto; com base na geometria do canal, o fluxo pode ser determinado a partir da altura. O sensor ultrassônico geralmente também possui um sensor de temperatura porque a velocidade do som no ar é afetada pela temperatura.

TDS-100H Medidor ultrassônico de vazão portátil

O medidor ultrassônico de vazão TDS-100H foi projetado para medir a velocidade do fluido dentro de uma tubulação. Os transdutores são do tipo clamp-on sem contato, o que proporcionará facilidade de instalação, operação e manutenção.

O TDS-100H funciona por tempo de trânsito e utiliza dois transdutores que funcionam como transmissores e receptores ultrassônicos. Os transdutores são fixados na parte externa de um tubo fechado a uma distância específica um do outro. Os transdutores podem ser montados em método V, onde o som atravessa o tubo duas vezes, ou pelo método W, onde o som atravessa o tubo quatro vezes, ou em método Z, onde os transdutores são montados em lados opostos do tubo e o som atravessa o tubo uma vez. Esta seleção do método de montagem depende das características do tubo e do líquido. O medidor de vazão opera transmitindo e recebendo alternadamente uma sequência de emissões de energia sonora modulada em frequência entre os dois transdutores e medindo o tempo de trânsito que leva para o som viajar entre os dois transdutores. A diferença no tempo de trânsito medido está direta e exatamente relacionada à velocidade do líquido na tubulação, conforme mostrado a figura.

TDS-100H Medidor ultrassônico de vazão portátil

 

Onde:

  • θ é o ângulo na direção do fluxo
  • M é o tempo de trânsito do feixe de ultrassom
  • D é diâmetro da tubulação
  • Tup é o tempo de trânsito do transdutor upstream até o transdutor downstream
  • Tdown é o tempo de trânsito do transdutor downstream até o transdutor upstream
  • ΔT=Tup -Tdown

Módulo principal do medidor de vazão

TDS-100H Medidor ultrassônico de vazão portátil

 

TDS-100H Medidor ultrassônico de vazão portátil TDS-100H Medidor ultrassônico de vazão portátil

Transdutores ultrassônicos

TDS-100H Medidor ultrassônico de vazão portátil

Aplicações do medidor de vazão ultrassônico

O medidor de vazão TDS-100H pode ser aplicado em uma ampla gama de medições em tubulações de 20 a 6.000 mm [0,5 a 200 polegadas]. É possível medir a vazão de diversos tipos de líquidos , como: líquidos puros, água potável, produtos químicos, esgoto bruto, água tratada, água de resfriamento, água bruta, efluente, etc. O medidor de vazão não é afetado pela pressão do sistema, sujeira ou desgastes. Os transdutores padrão são classificados para aplicações em até 110 graus centígrados. Temperaturas mais altas podem ser avaliadas sob consulta.

Retentividade dos dados e relógio de tempo real

Todos os valores de configuração inseridos pelo usuário são retidos na memória flash não volátil integrada, que pode armazená-los por mais de 100 anos, mesmo se a energia for perdida ou desligada. Para evitar alterações de configuração inadvertidas ou reinicializações do totalizador, a programação do instrumento é protegida por senha.

O instrumento é dotado de relógio de tempo real que permite acumular valores de vazão instantânea e de volumes totalizados formando um registro de valores no tempo. Ele continua operando enquanto a tensão da bateria for superior a 1,5V. Em caso de falha da bateria, o registro de dados não é garantido. O usuário deve reinserir os valores de tempo adequados caso a bateria fique totalmente esgotada. Um valor de tempo impróprio não afeta outras funções além dos registros no tempo.

Especificações técnicas do produto

Linearidade 0.5%
Repeatibilidade 0.2%
Precisão +1%
Tempo de resposta 0-999 segundos ( configurável)
Velocidade +32 m/s
Diâmetro da tubulação 20mm-6000mm
Unidade de medida Metros, pés, metros cúbicos, litros, pés cúbicos, galões USA, galões Ingleses, Barril de óle, Barril líquido, imperial liquid barrel, milhões de galões, configurável.
Totalizador 7 dígitos, positivo e negativo.
Tipos de líquido Virtualmente qualquer tipo de líquido
Segurança Senha de acesso para ajustes.
Display 4×16 para caracteres Inglês, 4×8 para caracteres chineses
Interface serial RS-232C, baud rate: de 75 a 57600 bps.  Protocolo próprio compatível com medidores de vazão FUJI. Outros protocolos sob consulta.
Transdutores Modelo M1 padrão, outros modelos sob consulta.
Comprimento dos cabos dos trandutores Padrão 2 x 10 metros.
Fonte de alimentação 3 baterias recarregáveis AAA Ni-H internas. 10 horas de operação. Carregador 100V-240VAC.
Data Logger Data logger interno para até 2000 registros de dados.
Totalizador manual Totalizador de 7 dígitos com zeramento pelo teclado.
Material do gabinete ABS
Dimensões do módulo portátil 100 x 66 x 20 mm
Peso do módulo portátil 514g (1.2 libras) baterias.

Composição do conjunto

O medidor de vazão é fornecido com acessórios e maleta.

TDS-100H Medidor ultrassônico de vazão portátil

TDS-100H Medidor ultrassônico de vazão portátil TDS-100H Medidor ultrassônico de vazão portátil

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O que é a TELEMETRIA DE ÁGUA E ESGOTO com LoraWan?

Trata-se de um sistema eletrônico de automação, monitoração e controle dos reservatórios e estações elevatórias de água e esgoto, ETAs (Estações de Tratamento de Água), ETEs (Estações de Tratamento de Esgoto) e demais pontos de interesse como Boosters (Estações de Pressurização), VRPs (Válvulas Reguladoras de Pressão) e pontos de medição de pressão e vazão da rede de distribuição de água tratada. Todo o controle se dá no CCO (Centro de Controle e Operação).

Por que implantar a telemetria com LoraWan?

Em um município sem sistema de telemetria, é a população que avisa a companhia de água e esgoto quando ocorre uma falha no abastecimento.

O sistema de automação e telemetria com LoraWan é necessário para:

  • Garantir o abastecimento da população;
  • Monitorar em tempo real o funcionamento de estações elevatórias, reservatórios, medidores de vazão e demais dispositivos elétricos e hidráulicos do sistema;
  • Armazenar e apresentar dados históricos sobre a qualidade do abastecimento;
  • Alarmar vazamentos, falhas de operação, falhas de equipamentos, intrusões, valores anormais de níveis, pressões e vazões;
  • Prevenir e minimizar perdas;
  • Enfim, garantir a qualidade dos serviços prestados.

O que é a tecnologia LoraWan?

LoRa é uma tecnologia sem fio, assim como o Wi-Fi, LTE, NB-IoT, entre outras. Seu potencial é infinito e foi criado para sua aplicação em IoT. LoRa deriva de (Long Range wireless communication) – Comunicação sem fio de longo alcance. Entre muitas de suas vantagens está a ampla faixa de cobertura e o baixo consumo de energia que proporciona. É a opção perfeita para soluções que requerem baixa largura de banda de dados e operação autônoma de longa duração, como é o caso da telemetria do saneamento.

O que é LoraWAN?

LoraWAN é o protocolo de rede que utiliza a tecnologia Lora. Esse protocolo é a camada superior da comunicação LoRa, e utiliza Media Access Control (MAC). LoraWAN é a camada de software que define como os dispositivos conectados usam a tecnologia LoRa. LoraWAN define os formatos de mensagem e a forma como as mensagens são trocadas entre os componentes da rede.

Como funciona a telemetria do saneamento com a tecnologia LoraWan?

O sistema de telemetria é composto por unidades remotas e por um CCO (Centro de Controle e Operação.

Dotado de computadores e monitores, o CCO permite que a equipe de operação supervisione e controle o funcionamento de todo o sistema de abastecimento de água do município. Do centro de operações é possível comandar de forma automática e manual o funcionamento de elevatórias, reservatórios, boosters, válvulas, comportas, macro medidores de vazão e qualquer outro dispositivo eletromecânico. Toda a comunicação se dá via rádio.

A comunicação entre as unidades remotas e CCO se pela aplicação de gateways Lora que transmitem e recebem dados da nuvem LoraWAN, através de concentradores de comunicação públicos ou privados.

Unidade remota de telemetria de reservatório com LoraWan

A forma mais usual para garantir o abastecimento de água em um bairro ou região de um município consiste em construir reservatórios em pontos elevados da área atendida, ou construir reservatório elevados quando a região é plana. A água é conduzida aos pontos de consumo por gravidade e o sistema de abastecimento municipal tem como missão, manter os reservatórios abastecidos.

Unidade remota de telemetria de elevatória com LoraWan

Cabe à estação elevatória de água a função de manter o reservatório abastecido. Para tanto, a informação do nível do reservatório deve ser transmitida à elevatória para que essa, por sua vez, comande o funcionamento dos grupos moto bombas de maneira a manter o reservatório sempre com o nível dentro dos níveis predefinidos de operação.

A informação de nível de cada reservatório é repassada à sua respectiva estação elevatória pelo sistema da comunicação via rádio, centralizado no CCO.

Nesse tipo de configuração o reservatório terá dois níveis (set points) pré-definidos pela operação:

  • Nível de liga: O nível de liga é mais baixo que o nível de desliga e é aquele nível, que quando atingido, indica para a lógica de comando da elevatória que o grupo moto-bomba deve ser ligado.
  • Nível de desliga: O nível de desliga é mais alto que o nível de liga e é aquele nível, que quando atingido, indica para a lógica de comando da elevatória que o grupo moto-bomba deve ser desligado.

A tecnologia LoraWan na telemetria do saneamento

A figura acima apresenta uma topologia típica de uma elevatória de água tratada  de um sistema de distribuição de água tratada municipal. O diagrama mostra os componentes básicos de uma elevatória composta por dois conjuntos moto bomba, principal e reserva, e apresenta também o reservatório abastecido por essa elevatória, que pode estar distante quilômetros da elevatória.

Painel de telemetria com LoraWan

A figura a seguir mostra um exemplo de unidade remota de telemetria utilizada na automação da estação elevatória e reservatórios.

A tecnologia LoraWan na telemetria do saneamento

RAK7431 – Rádio modem LoraWan RS485

RAK7431 - Rádio modem LoraWan RS485

RAK7431 – Rádio modem LoraWan RS485

RAK7431 WisNode Bridge Serial é um conversor RS485 para LoRaWAN projetado para aplicações industriais. O dispositivo retransmite dados ModBUS usando a rede LoRaWAN como meio de transmissão sem fio de e para os dispositivos finais.

O RAK7431 pode operar em todas as bandas LoRaWAN dentro dos parâmetros padrão definidos pela LoRa Alliance. Seu alcance em ambiente aberto é de mais de 15 km e em casos industriais, onde existem obstruções pesadas no caminho do sinal de RF, o desempenho é melhorado em comparação aos sistemas sem fio convencionais devido às características do LoRa como técnica de modulação. Isso permite uma qualidade de sinal consistentemente boa dentro dos limites de grandes fábricas, escritórios densamente povoados, armazéns, etc.

Estes dispositivos compatíveis com RS485 podem endereçar até 16 nós terminais de clientes. A conversão de e para estruturas LoRa é perfeita e permite controle e monitoramento em tempo real de vários dispositivos RS485, para acessar e controlar os nós terminais RS485.

Plataforma Eagle IoT industrial

Eagle - Plataforma IoT industrial

É um conjunto de soluções de hardware e software com a tecnologia Internet das Coisas (IoT) e foco na Gestão de Utilidades e Gestão de Ativos. A Plataforma Eagle IoT industrial foi desenvolvida para:

  • Redução de Custos Operacional;
  • Manutenção preventiva e preditiva;
  • Disponibilização de informações para a tomada de decisão.

A solução permite coletar informação em tempo real, a baixo custo e com agilidade e flexibilidade, para ganho de eficiência.

Áreas de aplicação da Plataforma Eagle IoT industrial

  • Grupos geradores;
  • Usinas solares;
  • Energia;
  • Iluminação;
  • Saneamento;
  • Climatização;
  • No-breaks;
  • Sistemas de aquecimento;
  • Gestão de utilidades.

Topologia da Plataforma Eagle IoT Industrial

Eagle - Plataforma IoT industrial

Gateways IG-8K e IG-9K

Eagle - Plataforma IoT industrialOs gateways Eagle são gateways WIFI/Ethernet/Celular para comunicação com equipamentos dotados de comunicação MODBUS e publicação dos dados coletados junto a eles a um broker MQTT.

Os mesmos podem operar, também, em modo Transparente (Bridge) em conjunto com sistemas on-premise, tornando bidirecional a comunicação no parque instalado, bem como coletar informações medidores de energia para posterior publicação.

Os gateways possuem FOTA (Firmware Over-The-Air ), possibilitando atualização remota sem necessidade de cabos e softwares de programação, auxiliando na manutenção à distância, de todos os gateways instalados em campo.

Conectividade

WiFi (802.11 b/g/n) – Utilizando antena externa 1, é possível estabelecer conexão sem fios à redes locais utilizando IP Fixo ou Dinâmico (DHCP).
Fast Ethernet (100Mbps) – Através do conector RJ45, o gateway pode se conectar a uma rede Ethernet cabeada, obtendo IP Fixo ou Dinâmico (DHCP).
Rede Celular (LTE, CAT-M1, NBIoT, 2G, 4G e pronto para o 5G) – IG-9k/M possui conexão com redes celulares, sendo capaz de utilizar os mesmos protocolos das redes WiFi e ETH.

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When I started my journey into industrial automation 28 years ago, some models of PLC models still used EPROM memories. In other words, it was necessary to write the program, compile, write the EPROM, insert the EPROM into the socket, and test the change. I used to have half a dozen EPROMs in the eraser to keep […]

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This article is the first of a series in which we share all the knowledge we have accumulated over more than 25 years supplying automation and telemetry systems for water and sewage in municipalities from north to south of Brazil. If you want to design and implement a telemetry system for water and wastewater reservoirs […]

Descrição geral do sensor DS18B20   O DS18B20 é um sensor de temperatura da Dallas/Maxim com saída digital programável de 9 a 12 bits. Contém também uma função de alarme, também programável, cujos dados são armazenados em uma área não volátil  de memória EEPROM. A comunicação entre o microcontrolador e o sensor se dá sobre um […]

Fonte (Automazione Industriale n.268 – Dicembre 2018) – Tradução e Adaptação: Eduardo Grachten Empresas italianas estão usufruindo das vantagens decorrentes da integração de conhecimentos que antigamente eram distantes e hoje são combinados pela mecatrônica Autor – Massimiliano Cassinelli Sobre o significado do termo mecatrônica já se discute há algum tempo, até porque a origem dessa […]

Os sistemas de transportes foram grandemente melhorados em 1998 quando a EPTC de Porto Alegre adotou uma nova tecnologia para controlar a qualidade dos serviços prestados pelas empresas de ônibus da cidade o SOMA – Sistema de Ônibus Monitorado Automaticamente. O sistema é constituído de 52 estações de monitoração distribuídas pela cidade, que registram a passagem […]

WorkSense W-01 WorkSense W-01 é o novo robô de dois braços da Epson apresentado pela primeira vez na Europa durante a feira AUTOMÁTICA 2018 que acontece em Mônaco, na Baviera, de 19 a 22 de junho de 2018. Fonte – Automazione Industriale – https://www.automazioneindustriale.com/il-robot-dual-arm-di-epson-che-vede-rileva-pensa-e-lavora/   Ideal para a automatização de atividades complexas em espaços reduzidos, o […]

Fonte – Automazione Industriale No. 260 – https://www.automazioneindustriale.com/ Os COBOTS – Robôs Colaborativos – estão cada dia mais presentes no processo produtivo. Encontramos os principais fabricantes do setor para entender essa novidade e suas consequências no ambiente de trabalho. Na Itália, já existe um robô para cada 62,5 operários. Trata-se de um número significativo, sobretudo […]

Por que a telemetria de água e esgoto é importante? Se você reside em um dos 5.570 municípios brasileiros este assunto é importante para você. Quando em uma cidade a população é quem avisa a empresa de águas do município sobre a falta de água, isso provavelmente se dá pelo fato de o município não possuir […]

Você que desenvolve soluções especiais para controle de processos e automação industrial irá gostar dos dispositivos apresentados abaixo. Todos foram criados para resolver problemas de campo que demandavam soluções criativas e inovadoras. Rádio modem para comunicar RS232 e RS485 em até 32 km O transceptor RM2060 consiste em uma solução de alto desempenho e baixo […]

Descubra como o SAEMAS no município de Sertãozinho no interior de São Paulo viabilizou o sistema de telemetria da distribuição de água tratada do município com a ajuda da FEHIDRO e da ALFACOMP. FEHIDRO  O Fundo Estadual de Recursos Hídricos apoia os estudos, a implementação e a manutenção de projetos de aproveitamento e gestão dos recursos hídricos […]

Introdução Estamos vivendo no Brasil um momento crítico em termos de abastecimento de água e energia. Resultado de um modelo econômico que incentivou o consumo e não o investimento, estamos próximos do colapso no abastecimento de energia elétrica. De outro lado, fruto de fenômenos climáticos, agravado pela falta de políticas públicas, o país vive a […]