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Due to the constant increase of the electricity price, all types of customers must find new formulas to reduce their electricity bill. To succeed in this, we are presenting our new power management system to control the maximum demand: MDC series (MDC 4 and MDC 20).

How to understand the electricity bill

It is necessary to understand the different terms which appear in an electricity bill to identify where we can act to reduce it. Of all the concepts, the most important ones are: Active energy term, reactive energy term and, in some countries, the maximum demand term, being this one last the subject of this article.

As described below, an optimal management of the contracted power allows us to:

  • Adjust the installation to the real demand by reducing the contracted power
  • Avoid maximum demand penalties due to a power excess
Spanish bill simulation
Spanish bill simulation

Active energy term
Consumption of active energy (kWh), applying different tariffs and rates

Maximum demand term or Maximum demand indicator (MDI)
Maximum demand register (kW or kVA). This is the maximum power value, usually the average of 15 minutes, reached during the billing period (this average time may vary depending on the country). Once the value is higher than the contracted power, the customer will pay a penalty on the electricity bill.

Reactive energy term
Consumption of reactive energy (kVArh), applying different tariffs and rates. Depending on the cosϕ value, the user will pay a penalty (this penalty is not applied in all countries)

Maximum demand calculation

The maximum demand value is the average from the instantaneous power (in kW or kVA) during a defined time interval, usually every 15 minutes (this time interval will depend on each country). There are different methods to calculate this parameter:

Fixed window (Block window)

This is the maximum demand calculation during a defined interval (usually every 15 minutes). Once the data is obtained, the value is stored and it makes a reset to start a new calculation for the next 15 minutes. This 4 registers will be measured every hour.

Sliding Window

This is the maximum demand calculation during a defined interval (usually every 15 minutes). Once the data is obtained, it will wait one minute to start a new 15 minutes calculation (this time may vary depending on the country). This means that every minute (this time can depends on the meter) it will record one maximum demand value from the last 15-minute period. This 60 registers will be measured every hour.

What can we do to avoid maximum demand penalties on the electricity bill?

To avoid penalties for maximum demand we must ensure that this value will never exceed contracted power.

Usually in electricity bills, the highest maximum demand value recorded by the meter is compared to the contracted power. Whenever this value is higher than the contracted power, there will be an economic penalty. Therefore, if during the billing month the power exceeds the one contracted, during a period of 15 minutes, the customer will pay a penalty, even if it exceeds only once a month (one month has approximately 2880 fifteen-minute periods).

For the particular case of Spain, depending on the maximum demand value, the penalty can involve a very significant bill increase, as described in the following graph:

Maximum demand term increase depending on the Contracted power exceeds (Spain- for tariffs 3.0 and 3.1)
Maximum demand term increase depending on the Contracted power exceeds (Spain- for tariffs 3.0 and 3.1)

As shown in the graph, if the maximum demand value exceeds 10 % of the contracted power, the user will pay a 20% increase on the maximum demand term. However if the maximum demand value exceeds 20 % of the contracted power, the user will pay a 50% increase on the maximum demand term.

How to control the Maximum Demand value?

As we have been advancing, the goal to control the maximum demand is to not exceed the limit of the contracted power. To archive this goal, we advise to install a system able to disconnect non critical loads, on different time periods, and also avoid connecting loads simultaneously to reduce the instantaneous power.

Non-critical loads are those that do not affect the main production process or that are not essential, such as:

  • Lighting
  • Compressors
  • Air-conditioning systems
  • Pumps
  • Fans and extractors
  • Packaging machines
  • Shredders
  • others

Which devices help us avoid maximum demand penalties?

The main objective of the new CIRCUTOR MDC series is to manage and control the maximum demand of an installation. To achieve this objective, the device connects and disconnects some loads (non-critical ones) to ensure that the maximum demand will never be higher than the contracted power, avoiding electricity bill surprises. Moreover, the extended MDC 20 range, allows a tariff control to adjust the loads for being connected on periods with lower price, avoiding high consumptions due to loads simultaneity during high tariff price periods.

MDC 4 device
MDC 20
MDC 20 device

Small and medium-sized industries solution

MDC 4: Analyzer to control the maximum demand level

MDC 4 is perfect for those installations which need a basic maximum demand control. Following some easy configuration steps the user will define up to 4 maximum power levels to start disconnecting non-critical loads.

Furthermore, MDC 4 incorporates an internal power analyzer for the maximum demand calculation (it also records electrical parameters such as voltage, current and power). Every time MDC 4 detects a power excess, this will disconnect several lines with non-critical loads, reducing automatically the instantaneous power. This will ensure that the installation will not exceed the maximum demand limit, hence avoiding penalties on the next electricity bill.

Operation method of MDC 4

Operation method of MDC 4

  • Avoids maximum demand penalties
  • Avoids power peaks due to simultaneity while connecting loads
  • Helps to adjust the contracted power to the real situation
  • Manages up to 4 relay outputs
  • Built in power analyzer
  • Internal clock for power synchronization

Infrastructures and big-sized industries solution

MDC 20: Data logger to manage and control the maximum demand with integrated web server 

MDC 20 is a data logger with an integrated web server meant to manage and control the maximum demand. Its versatility allows the user to do basic or advanced configurations. MDC 20 manages non-critical loads to ensure that the maximum demand value will never exceed the contracted power, avoiding penalties for power excess.

MDC 20 has an Ethernet port and a RS-485 communication channel (Modbus RTU), 6 relay outputs for load management and 8 digital inputs for collecting pulses (from other meters) or for logical states (opened-closed). It is expandable up to 48 relay outputs and 48 digital inputs by connecting 12 LM 4I/O devices via RS-485 communications (with 4 inputs/outputs each one).

The device has an internal data base (more than one year of data) with an integrated web server with PowerStudio software for programming, configuring and monitoring the device status and the associated peripheral devices connected by RS-485. Furthermore, it graphically shows the simulation of the system behavior according to the programmed settings.

MDC 20 infrastructure

MDC 20 infrastructure

MDC 20
MDC 20
  • Avoids maximum demand penalties
  • Manages 6 relay outputs and 8 digital inputs
  • Expandable up to 48 inputs/outputs by RS-485 communications (installing LM 4 I/O devices)
  • Connection/disconnection of loads according to programmed priority
  • Versatile maximum demand control depending on conditions, using calendars, profiles, etc.
  • Simulation of system performance according to the device’s programming
  • Sends e-mails with customized messages
  • Stores more than one year of data
  • Compatible with any XML communication master
  • Creates and registers customized variables defined by the user (EnPI, %, Kg, CO2, Euros, …)

Click here to obtain more information about MDC 4 and MDC 20

New MDC series to manage and control the maximum demand

You can also follow our publications on CIRCUTOR's Twitter account, and on LinkedIn.





  • 需求波动速率
  • 系统平衡
  • 谐波失真等级


当我们进行感性无功电能补偿时,将电容柜并联在逻辑上会抑制这一需求,将预期的视在功率 (kVA) 拉近到有功功率 (kW) 来实现方案要达到的目的。这一简单的概念可被总结为感性(L –互感器和电网) 和容性(C- 电容柜)电路的并联。schematics and resonance curve





1. 整流器
2. 焊接机
3. 变速机
4. UPS
5. 放电灯
6. 个人电脑


  • 整个系统的电压失真放大(这将会损伤设备和敏感电器元件)。
  • 电容器大量吸收电流,会导致间接发热,容量衰减并缩短使用寿命,并且导致电容器损坏。




他选择了采购传统电容柜和150 kvar开关柜。



THD(U)% and THD(I)% schematics indicating the capacitor bank connected and disconnected

THD(U)% 和 THD(I)%指示电容柜的连接与断开

虽然系统看出了相对较低等级的电流失真(7-8% THD(I)% 在400 A 时)但电压等级并未被察觉( 3.3% THD(U)% )。根据经验,系统中可能存在的共振在THD(I)% 的 15% 以及THD(U)% 的 2% (没有关于这一现象的相关规定)。

我们手动将各个电容柜投入后观察THD(U)%值是怎样上升的。这是并联共振产生的主要标志。投入电容柜后,工厂内满负载情况下THD(I)%达到了80% ,THD(U)%达到23%, (graphic 1)。有一个想法是将所用的供电电压质量限制为8% (UNE EN-50160)。

Without capacitor bank connected


With capacitor bank connected

项目 单位 金额
传统的 150 kvar 电池 1 4.400 €
400 V 电容器更换 9 3.056,50 €
460 V 电容器更换 6 2.474 €
人工成本 (预估为 20 €/h) 19 380 €
导致停机及处理 (预估为 2,500 €/h) 2,5 6.250 €
无功电能附加费(平均每月为 958 €/月) 2 1.916 €
FR型失谐电容柜 1 12.285 €
总成本   30.761,50 €


pdf 下载这篇文章的PDF 版本


Francesc Fornieles Castells
Responsable de Mercados - División Calidad de Red
市场部经理 - 电能质量部门



Energy control and Management

Example of energy savings at a Citroën car dealership

3SL Aplicaciones Integrales Eléctricas (Integral Power Applications), is a company that specialises in electrical installations. Major increases in electrical energy costs and the demand from the internal market have led us to specialise in energy consulting services to enable us to offer our clients greater returns from their installations.


Type of installation:

  • m2 of showroom space: 1.305
  • m2 of workshops: 4.085
  • m2 of offices: 330
  • m2 of warehouse: 500
  • Access tariff: 3.0 A
  • Utility company: Endesa
  • Contracted power: 175 kW
  • Annual consumption in kW-euros 2012: 260.000 kW – 55.000€ approx.

Since its creation some 5 years ago, our technical team has been constantly working on the development and implementation of an energy control system for electrical, gas, air, nitrogen and other energy sources that can make the maximum effective use of energy consumption at installations.

Installed units are provided with WEB-based remote control systems that enable us to store all the data on a secure server for subsequent processing; the data is then analysed to see what measures can be applied to the units to achieve the greatest possible efficiency. This process leads to sizeable energy savings, which in turn create savings in overall costs.

For example: an installation that operates as a car dealership, with a

  • Showroom of 1,305 m2
  • Workshop surface area of 4,085 m2
  • Office surface area of 330 m2
  • Warehouse surface area of 500 m2

To analyse the client's installation we install units manufactured by CIRCUTOR. A prior visual inspection of the installations is performed to establish the most critical points in terms of consumption. The car showroom area where customers are attended is the most complicated one to acclimatise because of the m2 and the solar orientation, and so we decided to control the area's air conditioning and lighting consumption.

 Based on the consumption of our installations we can determine the carbon footprint that we are leaving in the atmosphere
Based on the consumption of our installations we can determine the "carbon footprint" that we are leaving in the atmosphere

We then decided to control overall consumption by installing CIRCUTOR units in the general switchboard to compare real readings with those billed by the utility company, control reactive energy, power demand, etc.

The investment made in control and management units is approximately 4,000€, and consists of an EDS control unit and 4 CVM MINI analyzers in the air conditioning panel.

Example of a single screen of CIRCUTOR PowerStudio energy control software
Example of how on a single screen of CIRCUTOR PowerStudio energy control software we can control:
• General consumption
• Air-conditioning unit consumption
• Showroom lighting consumption
• Exterior and showroom temperature

An investment of approximately 5,000€ divided into three blocks has been made in the improvement section: firstly, improvements in air conditioning control with the physical installation of temperature probes and control relays for the start-up of the air conditioning units.

The second block consists of technical support for temperature programming and automatic operating schedules of the machinery, along with WEB-based control of every parameter and on-line alarm generation.

The third block consists of the installation of a power factor correction bank to eliminate unwanted generation. An investment return period of less than one year was calculated.

One of the major pluses of this system is that the user can consult the status of the installation any time, anywhere and can even take appropriate measures, he can also receive pre-defined alarm e-mails and so anticipate future breakdowns or excessive energy bills.

The results are really encouraging, a reduction of 11% to 24% is already being achieved; real data for 2012-2013.

The figures for the month of August are quite spectacular, the organisation obtained savings (compared to the same month in the previous year) of 28.74%, which represents 1,879.27€, at the same level of business activity as the year before.

 CIRCUTOR's EDS, CVM MINI and theOPTIM Series capacitor bank are theproducts used in the car dealership'sinstallation to improve efficiency andsave energy.

CIRCUTOR's EDS, CVM MINI and the OPTIM Series capacitor
bank are the products used in the car dealership's
installation to improve efficiency and save energy.

EDS / EDS 3G, New Data Logger with built-in Web Server Auditing 365 days a year

Is a simple, powerful industrial device, able to display, through its built-in Web and XML Server, all the electric variables from power analyzers or other field devices directly related to measuring consumption, electricity, water, gas, etc.

CVM MINI, Three-phase electrical power analyzer

The ONLY analyzer suitable for DIN rail distribution boards, only 3 modules

Measures, calculates and displays in true effective value (TRMS) the main electrical parameters for balanced and unbalanced, three-phase electrical systems.

OPTIM 1, Capacitor bank

The OPTIM series automatic capacitor banks are units designed for automatic reactive energy compensation in networks with fluctuating loads and power variations lasting seconds, through operations carried out by contactors.

Its simple installation, high technology and robustness make the OPTIM series the ideal units for compensating reactive energy in installations with fluctuating load levels.



New electrical parameter monitoring units can be used to check the following:

  • The distribution of consumption (what and how much is consumed)
  • The load profile (when consumption takes place)

The appropriate measures can be taken with this information, these reports and graphics to:

  • Permanently optimise and control installations, which facilitates their maintenance and improves their reliability
  • Achieve important savings and reduce the annual electrical energy bill
  • Forecast and check consumption and the electrical energy bill, i.e., general consumption and consumption distributed by use (lighting, air-conditioning, driving power, etc.)

However, the actions described in this report forecast savings of 11 to 24%, but we also have access to "Dossier-3SL-VEHICLE EXHIBITION AND SALE PLANT", from which we can calculate a 61% profitability (annual savings of 13,000 euros) of the investment, representing savings of 23.6% of the annual electricity bill over the total consumption of the plant..


Total reactive energy consumption in Euros

Total reactive energy consumption in Euros
To eliminate reactive energy generation and expense, a CIRCUTOR OPTIM series capacitor bank was installed for power factor correction.
An investment return period of less than one year was calculated.

Total electrical energy consumption in Euros

Total electrical energy consumption in Euros
Comparison of energy savings in euros for 2012 and 2013.
Reductions of 11% to 24% were achieved
We can see that electrical energy consumption in euros have decreased since June (installation date of the complete energy savings system); the same change can be seen in the reactive energy consumption graphic.
Reductions of 11% to 24% were achieved

pdf Download this article in PDF format


RGU-2 漏电保护继电器

1.- Summary:

Earth leakage protections are challenged, due to the continuing growth of complexity in electrical facilities and new regulations.
In this article a guest technical expert explains the new RGU-2 device, ready for these challenges, that increases productivity and saves in maintenance of facilities.


2.- Introduction:

The majority of electrical installations nowadays increasingly include loads that incorporate electronics.

Loads with electronics influence the electrical installation in various ways:

  • They generate harmonic distortion in the current they consume.
  • They generate current leakages at the mains frequency, 50 Hz, and at higher frequencies under normal operating conditions.
  • As soon as they are connected to the electrical power supply they generate a leakage current point.
  • During an insulation fault, the leakage current might not be sinusoidal, but rather pulsating, for example.

Examples of units incorporating electronics:

Computers, low consumption light bulbs, ceramic hobs, washing machines, dishwashers, microwaves, mobile phone chargers, air conditioning units, electric vehicle chargers, dryers, machine tools, etc.

Under normal conditions all these receivers generate leakage current in the electrical installation which makes the earth leakage protection more prone to trip.

3.- RGU-2 Earth leakage

The new RGU-2 unit provides the following technical details that help us maintain a protected installation and at the same time avoid unwanted tripping of the earth leakage protection, therefore supply has more guarantee.

Trip range:

The manufacturing standard for earth leakage establishes that the trip range must be between 50% and 100% of the sensitivity, for example, an earth leakage of 30 mA should trip between 15 and 30 mA.

What happens if we have an earth leakage with a trip sensitivity at 16 mA and another at 25 mA?

  • The two earth leakages comply with current legislation.
  • The first one will trip before the second.
  • If we also assert that there is always a leakage current in an installation without any malfunction, the first will always be much more prone to trip.
  • If at the moment the power supply connection is made we have a transient leakage current, it is much more likely that the more sensitive one will trip sooner.

What the RGU-2 provides:

  • It has a trip range of between 85% and 100% of its sensitivity.
  • Therefore, it guarantees a greater, more robust and reliable supply.
Trip range
Earth leakage
sensitivity [mA] 
Standard earth 
leakages [mA]
RGU-2 Earth
leakage [mA]
30 15 - 30 25 - 30
300  150 - 300 255 - 300
500 250 - 500 425 - 500
1000 500 - 1000 850 - 1000

Earth leakage type:

The most commonly installed earth leakages are type AC, but they only detect 50 Hz alternating leakage currents. Therefore they are not suitable when there are loads with electronics.

These units are marked with the symbol:

Class AC

The RGU-2 unit is capable of detecting pulsating and alternating leakage current, and it is classified as type A.

Type A units are marked with the following symbol:

Class A

Therefore, the RGU-2 provides our installation more security, and can detect both a pulsating and alternating leakage current.

Sensitivity with the frequency:

Another important detail is knowing how the earth leakage behaves with the frequency. Normal earth leakages are more sensitive to 50 Hz alternating current.

This would be enough if the facility did not have electronic loads.

The RGU-2, besides being sensitive to 50 Hz current, is less sensitive to higher frequency currents. Initially this might not appear as something good for electrical safety, but that is not entirely true.

We need to bear in mind that:

  • receivers that incorporate electronics generate high frequency leakages.
  • The human body is more sensitive to 50 Hz than 500 Hz. That means that the higher the frequency the more current is needed to produce the same effects.

International standard IEC 479-2 states the current values that a person can withstand depends on the current frequency. The RGU-2 earth leakage adjusts its sensitivity to the limits established by the safety standard.

Another important factor deduced from the response to high frequency is that it results in stronger immunity to inopportune trips. Plus, if it has less sensitivity at higher frequency, it means that in the end the earth leakage is more robust to any transient disturbances that could reach us through the electrical network itself.

Concept of Ultra-immunisation:

The RGU-2 is an ultra-immunised earth leakage!
But what does that mean and what does it add to our installation?

Ultra-immunised earth leakages protections are popularly known as ones that do not trip because of false alarms, or which are quite hard to trip inopportunely.

Where do these qualities come from? Well, basically from the data we have already described and which we summarise once more time:

  • Trip range between 85% and 100% of the sensitivity.
  • Frequency response, in particular reducing sensitivity when frequency increases.
  • Higher immunity to network transients

Other features of the RGU-2:

The new RGU-2 provides the following features:

  • Clear, simple display with a led bar graph or with an indicator of the exact leakage value on the LCD screen.
  • Wide range of external toroidals.
  • Sensitivity settings: 30, 100, 300, 500 mA, 1, 2, 3, 5 A.
  • Adjustable trip time: Instantaneous, Selective, 0.1, 0.2, 0.3, 0.5, 1, 2, 3, 5 Seconds.
  • 2 relay outputs for indicating pre-alarm and alarm.

RGU-2 wiring diagram

All these features make possible to use the RGU-2 earth leakage relay for a wide range of applications, both for installation at the main panel, on sub-panels, and in the final load protection, as well as being valid for VT, TN-S and IT network regimes, including single-phase and three-phase with and without neutral.


Joan Romans Artigas
Electronics Engineer
Telecommunications Technical Engineer

Francesc Fornieles Castells
Responsable de Mercados - División Calidad de Red
Markets Manager - Power Quality Division


More information

CIRCUTOR opens here a section for clients and Partners to send technical articles, about their experience with CIRCUTOR's equipment and software. 
Articles must be written on a right technical level, in order to be published.



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