Residual Current Protection Relay and Toroid Current Transformers

Grounding measurement is of critical importance in every business and every moment of life, whether it is an industrial facility or an office building. Because grounding gives important clues about the health of a facility’s electrical system. For this reason, grounding measurement should be made regularly for each facility. On the other hand, the resistance values ​​of grounding equipment may change over time. This may cause current and voltage values ​​to exceed reliable values. Grounding also ensures the correct operation of protection elements in electrical systems. A good grounding system is very important for electrical protection systems such as residual current relay, surge arrester, thermal magnetic switch, automatic fuse to open at the desired value and on time. Improper grounding, which has different types such as protection, operation and lightning protection, varies according to its purpose. Improper grounding creates the danger of leakage current due to various isolation and insulation faults. In such cases, leakage current poses a great danger to living beings and the life of the electrical devices used.

What is Grounding? To answer your question;

grounding system; It can be defined as establishing a conductive connection between the designated touch points of panels, devices and machines and the ground electrode. This ground electrode (ground stake, ground plate, etc.) is buried in the ground as a conductive part and establishes an electrical connection with the ground.

GroundIt is the connection of the device body to the ground by establishing a conductive connection between the devices and the ground, in case of insulation failures that may occur in the devices. In this way, no problems arise for people because the fault current flows towards ground. If there is no grounding, fault currents will flow through the person touching this device, and death may occur depending on the level of this current. Therefore, thanks to grounding, leakage currents are safely directed to the ground and if an automatic tripping system (residual current relay etc.), electrical power is cut off safely.

Earth leakage current relaysare devices used to provide protection against earth leaks occurring in electrical circuits. These relays, which help prevent dangerous situations such as electric shock and fire, have a very important place in the protection system. Its operating principles are based on detecting current imbalances and protecting the circuit in case of ground leaks. If the value of the unbalanced current differences flowing through the circuit exceeds a certain threshold, the relay opens the circuit within the specified time and activates the protection mechanisms. In this way, dangerous situations that may arise from ground leaks can be prevented.Toroid current transformers (Core Balance Current Transformer, CBCT) are electrical devices consisting of windings wrapped around a toroidal core. These transformers also have advantages such as high efficiency and low magnetic leakage. Its operating principles are based on the transfer of electrical energy from the primary winding to the secondary winding through a magnetic field. Toroid current transformers are connected to the electrical system by passing 1-phase/neutral cables at low voltage level and 3-phase/neutral cables through the ring gap at medium voltage level.

Earth leakage current relaysIdeal protection system can be achieved by properly integrating with toroidal current transformers. Since the total phasor current will be zero under normal operating conditions, the net flux in the ring core will be zero and this will not create any current in the secondary of the toroid current transformer. In an unbalanced operating situation, as deviations will occur in the total phasor current, the net flux in the core will induce a leakage current in the secondary of the toroid current transformer. This will create a signal in the earth leakage current relay and trigger the opening of the relevant protection equipment.

The issue that should be considered when choosing Toroidal Current Transformers is that the total volumes of the phase and neutral conductors passing through the toroidal current transformer must be smaller than the internal volume of the toroidal current transformer. Since the only function of the toroidal current transformer is to measure the vector sum of phase and neutral currents, it does not have any breaking capacity value or nominal current value..

Residual current relay is a device used as a safety measure in electrical installations and its main purpose is to protect people against the risk of electric shock or fire. Residual current relay breaks or opens the main electrical circuit when it detects leakage current. The answer to the question of why the residual current relay trips is related to understanding the function and reasons of this relay. Here are some situations why the residual current relay may trip:

► Human contact: Residual current relay is used to prevent electric shocks that occur as a result of people coming into contact with electrical circuits. If a person touches a device or wire that carries an electric current, this relay detects that the current is not returning in the normal way and breaks the circuit, reducing the person’s risk of electric shock.

► insulation failure: Due to insulation faults or leaks in the electrical installation, electric current may pass illegally to the ground or other metal surfaces. Residual current relay detects such situations and breaks the circuit before a dangerous situation occurs.

► Device malfunctions: As a result of malfunctions in electrical devices or equipment, the outer surface or casing of the device may become current-carrying. This situation is detected by the leakage current relay and the circuit is interrupted.

► weather conditions: When electrical installations are exposed to outdoor conditions or water leaks occur, the risk of leakage current may increase. The leakage current relay detects the leakage current arising from installations or equipment exposed to water and breaks the circuit.

► Ywear and tear: Insulation of electrical installations or devices may weaken as a result of wear and tear over time, which increases the risk of leakage current. The residual current relay detects such situations and opens the circuit when necessary.

Residual current relay works sensitively against these and similar security threats and ensures that people stay safe. When the relay trips, it means that a potential hazard has been detected and intervention is required. Therefore, residual current relays are an important device to increase the safety of electrical installations.

ENTES ELR series earth leakage current relaysTogether with toroidal current transformers, it provides protection at different current levels and time resolutions. While it provides leakage current protection in the 30 mA-30A threshold value range, relay opening options are offered in the 0-10 sec time range. ELR, which can operate with both 50 Hz and 60 Hz frequencies, can be tested with the test/reset button and can be reset after switching on and made ready for use again. In addition, thanks to the LED indicators on the relay, it is possible to obtain information about the status and operating status of the device. The green indicator indicates that the relay is installed, and the red indicator indicates that a leakage current condition has occurred and the relay has been triggered. In addition to this; Information about the detected leakage current rate is provided by gradual green, yellow and red indicators. The ELR series has a compact and durable design that complies with international IEC60947 2/M standards. It is produced to withstand the harsh conditions of industrial environments under wide range temperature and humidity values.

It distinguishes itself from its competitors with its toroid model diversity, after-sales technical support, adjustable delay and sensitivity-customizable protection.

ENTES ELR-CBCT | Life-Saving Technology | First Line of Defense Against Electric Shock

 

Toroid current transformer (CBCT) is a ring type current transformer through which 3 Phase and 1 Neutral cables pass. This current transformer is normally used for residual current fault protection in low and medium voltage systems. The secondary of the CBCT is connected to the Earth Leakage Current Relay.

CBCT under normal conditions (Ia + Ib + Ic= 0)

The net flux in the core of the CBCT is zero. This means there is no secondary current. For this reason, the Earth Leakage Current Relay does not work.

During CBCT leakage current fault;

This is the situation where a 3-phase current passing through the center of the toroid current transformer cannot be balanced and zero net current will flow. Depending on the value of the net magnetic flux in the CBCT core, it will induce current in the secondary circuit where the leakage current relay will operate. For this reason, it is called Core Balance Current Transformer (Toroid Current Transformer).

► Wide Supply Range (220 – 415VAC / 220VDC)
► Manual and Automatic Reset Option
► Leakage Current Opening Time: 0sec-10sec
► TEST Feature to Check Functionality
► Leakage Current Trip Range: 30mA-30A
► CBCT Options:70mm, 92mm, 120mm, 210mmElectrical Connection for ELR and CBCT

► First the MCCB (compact switch trip coil) is connected to the circuit and the power comes to the MCCB circuit breaker first
► Then L1, L2, L3 and Neutral connections pass through the CBCT, and then they are connected to a load that we need to protect from leakage current.
► In order to get a response from the CBCT, the output of the CBCT is given to the B1 and B2 terminals of the ELR.
► ELR is supplied from terminals L1 and N or L1 and L2.
► So when there is a leakage current fault the CBCT will be active and respond to the ELR.
► For this reason, the normally closed contact becomes open.

ENTES offers residual current relays for different needs with its wide product range. ENTES residual current relays are designed and manufactured to provide reliable protection with high detection sensitivity, fast response time and robust structure. ENTES’ product range includes residual current relays with advanced features, developed especially for industrial facilities and large commercial buildings. These relays not only detect leakage current, but also offer the following features:► Leakage Current Adjustment: Depending on the need, the leakage current value can be adjusted between 30mA and 30A. This setting determines the sensitivity and trigger threshold of the device. For example, 30mA sensitivity is generally preferred to protect human life, while higher values ​​(e.g. 300mA) can be used for fire protection. With the adjustment buttons on the device, the relay can be turned off when the leakage current reaches a certain value.

► On Time Setting: If a current above the set leakage current value continues within the specified time, the relay gives the command to cut the circuit. You can adjust this time between 0 seconds and 10 seconds with the opening time setting. This setting is used to prevent unnecessary trips in some industrial applications where short-term leakage currents are considered normal.

► Test: After installing the relay properly, it must be tested. It helps verify the functionality and reliability of the device by checking whether the device detects the escaping current and closes the circuit by pressing the test button on the relay. This test should be performed periodically (e.g. once a month).

Using the earth leakage current relay correctly increases the safety of electrical installations and minimizes potential dangers in electrical systems. If you are in doubt about any installation or adjustment, it is important to seek help from an electrical professional.