Earth-Leakage Protection - ComPact NSX Legacy MicroLogic 5/6/7

Presentation

Earth-leakage protection on MicroLogic 7 trip units provides protection against low intensity fault currents to ground for:

All types of electrical distribution applications
People, according to the earth-leakage protection setting used

Earth-leakage protection is designed for installations with TT or TN-S grounding system.

The MicroLogic 7 electronic trip unit is available in two versions for earth-leakage detection:

The Trip version trips when earth-leakage is detected.
The Alarm version measures the earth-leakage current and indicates an earth-leakage fault on the display screen.

Operating Principle

Earth-leakage protection is definite time.

The earth-leakage protection threshold IΔn sets the level of earth-leakage current at which the circuit breaker trips when reaching the earth-leakage protection time delay Δt.

The earth-leakage protection settings are:

IΔn: earth-leakage protection pickup
Δt: earth-leakage protection time delay

Setting the Earth-Leakage Protection

Set the IΔn pickup with the MicroLogic 7 trip unit IΔn dial.

Set the Δt time delay as follows:

With the keypad on the MicroLogic 7 trip unit
With EcoStruxure Power Commission software (password-protected)

IΔn Pickup Setting Values

Trip unit rating In (A)	Pickup IΔn
IΔn dial position	1	2	3	4	5	6	7	8	9
40, 100, 160, and 250 A	30 mA	30 mA	100 mA	300 mA	500 mA	1 A	3 A	5 A	OFF
400 and 570 A ⁽¹⁾	300 mA	300 mA	500 mA	1 A	3 A	5 A	10 A	10 A	OFF
(1) Maximum setting at 570 A for thermal reasons, to be adapted with breaking block up to 630 A

The accuracy range is +/-10%.

Δt Time Delay Setting Values

When IΔn is set to the 30 mA, the earth-leakage protection acts immediately (instantaneous tripping), whatever the setting of the Δt time delay.

For other IΔn values (> 30 mA), the Δt time delay can be set to one of the following values:

0 s
60 ms
150 ms
500 ms
1 second

Testing the Earth-Leakage Protection (With Trip) Using Test Button

On the Trip version of MicroLogic 7 trip units, the earth-leakage protection must be tested regularly by using the test button T. Pressing the test button simulates a real leakage current passing through the toroid and the circuit breaker trips.

When the earth-leakage protection pickup IΔn is set to the OFF position, pressing the test button has no effect.

The earth-leakage function test can be performed with the padlock locked or unlocked .

Follow these steps to test and reset the earth-leakage protection on MicroLogic 7 trip units:

Step	Action	Display
1	Energize the circuit breaker.	–
2	Open the protective cover of the trip unit.	–
3	Provide a power supply to the trip unit so that the screen displays the result of the test after the circuit breaker trips.	–
4	Push the toggle handle from the O (OFF) position to the I (ON) position. The circuit breaker is closed.
5	Press the test button T: the circuit breaker trips. OK is displayed on the screen for two seconds and then the screen displays 0 A. NOTE: If the circuit breaker does not trip, the earth-leakage protection is no longer active. Analyze the cause and replace the MicroLogic 7 trip unit or the circuit breaker.
6	Push the toggle handle from the (Trip) position to the O (OFF) position.
7	Push the toggle handle from the O (OFF) position to the I (ON) position. The circuit breaker is closed.

Testing the Earth-Leakage Alarm (Without Trip) Using Test Button

On the Alarm version of the MicroLogic 7 trip unit, the earth-leakage alarm can be tested by using the test button T. Pressing the test button simulates a real leakage current passing through the toroid. The circuit breaker does not trip.

When the earth-leakage alarm pickup IΔn is set to the OFF position, pressing the test button has no effect.

The earth-leakage function test can be performed with the padlock locked or unlocked .

Follow these steps to test the earth-leakage alarm on MicroLogic 7AL trip units:

Step	Action	Display
1	Energize the circuit breaker.	–
2	Open the protective cover of the trip unit.	–
3	Provide a power supply to the trip unit.	–
4	Push the toggle handle from the O (OFF) position to the I (ON) position. The circuit breaker is closed.
5	Press the test button T: OK is displayed on the screen for two seconds, and then the previous screen is displayed. NOTE: If nOK is displayed on the screen, the earth-leakage alarm is no longer active. Replace the MicroLogic 7AL trip unit.

Testing the Earth-Leakage Function (Without Trip) Using Keypad Only

On the Trip and Alarm versions of the MicroLogic 7 trip unit, the earth-leakage tripping chain (or earth-leakage detection for the Alarm version) (except mechanism and pole operation) can be tested, without tripping the circuit breaker, by using the keypad.

The earth-leakage function test can be performed with the padlock locked or unlocked .

Follow these steps to test the earth-leakage protection alarm on MicroLogic 7AL trip units:

Step	Action	Using	Display
1	Select the earth-leakage measurement screen.
2	Access the earth-leakage function test by pressing OK. The tESt pictogram appears and the OK pictogram blinks.
3	Prompt the earth-leakage function test by pressing OK. The result of the test (OK or nOK) is displayed on the screen after two seconds. NOTE: If nOK is displayed on the screen, test the earth-leakage function by using the test button T.
4	After two seconds the screen returns to the screen displayed before the test	–	–

Earth-Leakage Test History

The last ten earth-leakage tests are recorded in an earth-leakage test history. Tests performed using the T test button and tests using the keypad are logged in the same history.

The history records:

Type of test: with trip or without trip
Date of test
Result of test (OK or nOK)

The earth-leakage test history can be consulted:

With EcoStruxure Power Commission software.
On a remote controller using the communication network.

Resetting the Circuit Breaker After an Earth-Leakage Fault Detection

Resetting the earth-leakage function after an earth-leakage fault detection (with or without trip) depends on the version:

For the Trip version, reset the circuit breaker by moving the handle from Trip to O (OFF) position, and then to I (ON) position. Acknowledge the earth-leakage trip screen by pressing OK.
For the Alarm version, acknowledge the earth-leakage trip screen by pressing OK.

Resetting the earth-leakage function after an earth-leakage protection test is described in the procedure for each test.