Stand-Alone USB Maintenance Interface

Introduction

Use the stand-alone USB maintenance interface for the following:

Maintenance checks and inspections
Tripping tests
The inhibition functions required for tripping tests by primary current injection

A USB maintenance interface kit comprising the USB maintenance interface and its accessories is available. For more information, refer to LVPED217032EN, ComPact NSX & NSXm Catalogue.

NOTE: The USB maintenance interface cannot be used with the MicroLogic 2.3 trip unit installed in a ComPact NSX400K circuit breaker.

Description of USB Maintenance Interface Kit

The USB maintenance interface kit comprises the following elements:

A USB maintenance interface

B Standard USB cord for connection to the PC

C Specific cord for connecting the USB maintenance interface to the test port on the trip unit

D Standard RJ45 cord for connecting the USB maintenance interface to a ULP module

E USB maintenance interface power supply unit

F Bluetooth/Modbus option for USB maintenance interface to be ordered separately.

Description of USB Maintenance Interface

A Mechanical cap in central position

B Green ON LED

C Test buttons (3) with LEDs (3)

D Connection socket for specific cord connecting USB maintenance interface to the test port on trip unit

E Connection socket for power supply unit

F Specific cord for connecting the USB maintenance interface to the test port on the trip unit

Preparing the Equipment

Prepare the equipment before carrying out maintenance:

Step	Action
1	Position the USB maintenance interface sliding mechanical cap in the central position.
2	Connect the 24 Vdc power cord: the green ON LED lights up.
3	Click the USB maintenance interface connector into the test port on the MicroLogic trip unit.

Inspection and Checking

Check and inspect the trip unit after preparing the equipment

Step	Action
1	Check that the green Ready LED on the MicroLogic trip unit is blinking. This means that all the MicroLogic trip unit functions are in a satisfactory operational state (internal self-test).
2	On the display unit for MicroLogic 5, 6, and 7 trip units, check the setting values by using the navigation buttons to display the Reading protection parameters mode. For more information, refer to DOCA0141EN, ComPact NSXMicroLogic 5/6/7 Electronic Trip Units - User Guide.
3	Scroll down and check the values of the different settings (for example, MicroLogic 5 trip unit): Ir (A) IN (A) (if present) long-time tr (s) Isd (A) IN (A) (if present) short-time tsd (ms) with/without I²t Ii (A) The settings can be modified.

Step

Action

Check that the green Ready LED on the MicroLogic trip unit is blinking.

This means that all the MicroLogic trip unit functions are in a satisfactory operational state (internal self-test).

On the display unit for MicroLogic 5, 6, and 7 trip units, check the setting values by using the navigation buttons to display the Reading protection parameters mode. For more information, refer to DOCA0141EN, ComPact NSXMicroLogic 5/6/7 Electronic Trip Units - User Guide.

Scroll down and check the values of the different settings (for example, MicroLogic 5 trip unit):

Ir (A)
IN (A) (if present) long-time
tr (s)
Isd (A)
IN (A) (if present) short-time
tsd (ms) with/without I²t
Ii (A)

The settings can be modified.

The Three Test Functions

Tests are carried out with the aid of the three test buttons. The associated LEDs provide confirmation.

A Electrical push-to-trip test button with pictogram and red confirmation LED

B Inhibit ground-fault protection button with pictogram and yellow confirmation LED

C Inhibit thermal memory button with pictogram and yellow confirmation LED

Tripping Test Using the Electrical Push-to-Trip Button

The electrical push-to-trip button causes an electronic trip in the circuit breaker. This test is used to check the electronic and mechanical circuit breaker controls.

Carry out the test after preparing the equipment:

Step	Action
1	Switch the circuit breaker to the I (ON) position.
2	To trip the circuit breaker, press the electrical push-to-trip button.
3	The red confirmation LED on the USB maintenance interface lights up and goes off immediately. The circuit breaker trips: The control mechanism moves to the tripped position: (with toggle handle), Trip (rotary handle), or OFF (motor mechanism). The green Ready LED on the MicroLogic trip unit continues blinking. The screen on MicroLogic 5, 6, and 7 trip unit stays unchanged.
4	Reset the control mechanism. The circuit breaker is ready.

Inhibit Ground-Fault Protection

The Inhibit ground-fault protection button temporarily cancels this protection (MicroLogic 6) and the thermal memory: it is then possible to inject the test current on each phase separately and calculate the true time delay tr.

Carry out the test after preparing the equipment:

Step	Action
1	Switch the circuit breaker to the I (ON) position.
2	Press the button to inhibit the ground-fault protection.
3	The yellow confirmation LEDs for ground-fault protection and thermal memory inhibition show a steady light. Ground-fault protection and the thermal memory on the trip unit are inhibited for 15 minutes.
4	Press the button to inhibit the ground-fault protection again (before 15 minutes).
5	The yellow confirmation LEDs for ground-fault protection and thermal memory inhibition go out. Ground-fault protection and the thermal memory on the trip unit are reactivated.

Inhibiting the ground-fault protection also causes the ZSI (Zone Selective Interlocking) function to be forced (if this option is present on the trip unit). This forcing prevents the time delay for short-time protection tsd from being taken out of commission during the tests.

NOTE: It is not possible to inhibit earth-leakage protection using the USB maintenance interface. Earth-leakage protection on MicroLogic 4 and 7 can be inhibited by turning the earth-leakage setting dial IΔn on the MicroLogic trip unit to the OFF position.

Inhibit Thermal Memory Function

The Inhibit thermal memory button temporarily cancels the thermal memory. This inhibition is necessary in order to obtain a true measurement of the long-time protection time delay tr during tripping tests by primary current injection.

Carry out the test after preparing the equipment:

Step	Action
1	Switch the circuit breaker to the I (ON) position.
2	Press the button to inhibit the thermal memory.
3	The yellow confirmation LED shows a steady light. The thermal memory on the trip unit is inhibited for 15 minutes.
4	Press the button to inhibit the thermal memory again (before 15 minutes).
5	The yellow confirmation LED goes out. The thermal memory on the trip unit is reactivated.

Inhibiting the thermal memory also restricts the ZSI function (if this option is present on the trip unit). This prevents the time delay for short-time protection tsd and time delay for ground-fault protection tg (MicroLogic 6) from being taken out of commission during the tests.