Earthing Fault Indicator (EFI) with auxiliary power supply
The EFI is designed to detect short circuits and earth faults in medium voltage networks.
It consists of an indicator unit in a housing for panel mounting (panel cutout size 92.5x45 +0.6 mm) and four current sensors connected to the measuring inputs of the device via optical fiber (included in the delivery).
It consists of an indicator unit in a housing for panel mounting (panel cutout size 92.5x45 +0.6 mm) and four current sensors connected to the measuring inputs of the device via optical fiber (included in the delivery).
Real-time temperature (T version)
The electronic current sensor detects the cable temperature during operation and transmits it in real-time to the host (indicator unit) via optical fiber.
The temperature is displayed on the screen of the indicator unit. If there is no fault, the temperature data will be uploaded every 15 minutes.
The temperature is displayed on the screen of the indicator unit. If there is no fault, the temperature data will be uploaded every 15 minutes.
Short-circuit alarm indication
When the phase line current reaches or exceeds the set short-circuit current value, the electronic current sensor sends an alarm signal, which is transmitted to the host (indicator unit) via optical fiber.
After the host receives this signal, the corresponding short-circuit fault indicator flashes. In addition, a signal is sent to the remote indication contact using the relay built into the unit.
After the host receives this signal, the corresponding short-circuit fault indicator flashes. In addition, a signal is sent to the remote indication contact using the relay built into the unit.
Temperature alarm indication (T version)
When the line temperature reaches or exceeds the set temperature value, the electronic current sensor sends an alarm signal, which is transmitted to the host via optical fiber, the host receives this signal, the backlight screen flashes, and then a temperature fault alarm signal is generated.
If another short circuit occurs during the reset time, for example, during the automatic reclosing process, the signal will be issued as double LED flashes. The following modes can be selected to reset the alarm:
The performance test is carried out by pressing the Test button and holding it for 3 seconds, the device will enter the self-test state, all indicators on the panel will flash, indicating that everything is working normally. The time of two adjacent self-test operations is from 2 to 5 seconds.
The automatic reset time is selected from the range of 6, 12, 24, and 48 hours and is determined by the customer before placing an order. By default, the automatic reset time is 12 hours.
The tripping time (delay) can vary from 25 ms to 3 s and is determined by the customer before placing an order. By default, the delay is 25 ms.
If another short circuit occurs during the reset time, for example, during the automatic reclosing process, the signal will be issued as double LED flashes. The following modes can be selected to reset the alarm:
- automatically, after the preset reset time has elapsed;
- by an external relay contact signal;
- manually by pressing the Reset button for 6 s.
The performance test is carried out by pressing the Test button and holding it for 3 seconds, the device will enter the self-test state, all indicators on the panel will flash, indicating that everything is working normally. The time of two adjacent self-test operations is from 2 to 5 seconds.
The automatic reset time is selected from the range of 6, 12, 24, and 48 hours and is determined by the customer before placing an order. By default, the automatic reset time is 12 hours.
The tripping time (delay) can vary from 25 ms to 3 s and is determined by the customer before placing an order. By default, the delay is 25 ms.
Technical specifications:
Parameter
Value
Tripping current setting (I)
200 A, 400 A, 500 A, 600 A, 800 A, 1000 A + 10%
Tripping time
delay 25 ms - 3 s (25 ms at 800 A by default)
Earth fault trip current setting (I0)
10 A, 20 A, 40 A, 50 A, 60 A, 80 A + 10%
Tripping time
delay 25 ms - 3 s (25 ms at 20 A by default)
Voltage
7.2-40.5 kV
Degree of protection
indicator unit IP40; current sensor IP65
Operating air temperature value
-40°C ~ 75°C
Max. cable diameter for installation of the short-circuit detection sensor (SK)
40 mm
Max. cable diameter for installation of the earth fault detection sensor (SE)
105 mm
Automatic reset time
6, 12 (by default), 24, 48 hours
Remote reset and remote transfer to standby mode
via an external non-latching contact
Indicator unit power supply
lithium battery, ER14505, 3.6 V, service life > 10 years, illumination for 1000 h
External power supply **
12-60 V DC, < 5 mA
Relay contact
30 V DC, 1 A
230 V AC, 0.5 A
230 V AC, 0.5 A
Number of operations
over 4000
Weight
420 g
Data transmission interface*, **
RS-485
Data transmission rate*,**
9600 baud
RS-485 auxiliary power supply voltage*
24-48 V DC
* for the indicator unit of M version - with the function of signal transmission via MODBUS through RS485.
** for the indicator unit of T version - with the function of temperature measurement and signal transmission via MODBUS through RS485.
** for the indicator unit of T version - with the function of temperature measurement and signal transmission via MODBUS through RS485.
The use of EFIs is a reliable, fast, and rational way to determine a fault and further localize it. In a ring power supply system, the faulty line sections are disconnected from the network as soon as the faulty section is detected. The section between the last tripped and the first non-tripped indicator is considered faulty. While the maintenance service is repairing the damaged cable, the rest of the equipment operates in normal mode. Thus, the disconnection time of the entire network is minimized. But even in networks with a radial power supply system, the fault indicator will help quickly find the damaged cable section without unnecessary switching of devices in the entire network.
Principle of operation
Transformer substation
Indicator triggered
Fault location
Indicator not triggered
Protection with circuit breaker
Fault indicators (earth fault and network short circuit) continuously poll the network status. As soon as the short-circuit current exceeds the detection threshold, an "error" signal will be issued. The output of the "error" signal is controlled by a microcontroller in order to avoid false tripping caused by transient processes in the network.
As a rule, the power supply in a ring power supply system is provided by 2 circuit breakers. There may also be a disconnector (switch) in the network. For the correct determination of the fault, indicators must be in each half-ring. In the future, when upgrading the system, the number of indicators can be increased.
In the event of a short circuit, all indicators located in the half-ring will trigger. But only the indicators located between the circuit breaker and the fault location will issue an "error" signal.
It is necessary to open the circuit breakers in the entire half-ring to prevent further damage to the cable or devices. Based on the indicator readings, the damaged cable section can be calculated. It will be located after the last indicator that issued an "error" signal and before the first non-triggered indicator.
After localizing the fault, the damaged cable must be replaced.
After disconnecting the damaged cable, the remaining consumers are reconnected to the network. Thus, the disconnection time of consumers is minimized, and the maintenance service can repair the damaged cable.
The reset of the alarm mode on the indicators can be done manually, as well as in automatic mode after applying voltage to the restored network section.
As a rule, the power supply in a ring power supply system is provided by 2 circuit breakers. There may also be a disconnector (switch) in the network. For the correct determination of the fault, indicators must be in each half-ring. In the future, when upgrading the system, the number of indicators can be increased.
In the event of a short circuit, all indicators located in the half-ring will trigger. But only the indicators located between the circuit breaker and the fault location will issue an "error" signal.
It is necessary to open the circuit breakers in the entire half-ring to prevent further damage to the cable or devices. Based on the indicator readings, the damaged cable section can be calculated. It will be located after the last indicator that issued an "error" signal and before the first non-triggered indicator.
After localizing the fault, the damaged cable must be replaced.
After disconnecting the damaged cable, the remaining consumers are reconnected to the network. Thus, the disconnection time of consumers is minimized, and the maintenance service can repair the damaged cable.
The reset of the alarm mode on the indicators can be done manually, as well as in automatic mode after applying voltage to the restored network section.