Long-Time Overcurrent Protection (L or ANSI 49RMS/51)
Presentation
Long-time overcurrent protection helps to protect cables, busbars, and busbar trunking against overloads, based on the true RMS current. It is implemented independently for each phase and for the neutral.
This protection function is an overcurrent time-dependent protection with thermal memory. It operates as a thermal image, using the heating and cooling model of a conductor. After tripping, the protection continues to integrate the cooling of the conductor.
This protection function can be used also for transformer or generator protection thanks to the wide range of settings offered.
Availability
Long-time overcurrent protection is available on:
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TS 2.0 and 2.0S, 5.0 and 5.0S, and 6.0S trip system
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3-pole and 4-pole circuit breakers
Long-time overcurrent protection is powered by the current flowing through the internal current transformers of the circuit breaker and it does not require additional external power supply.
Operating Principle
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Long-time overcurrent protection is based on the true RMS current of phases and neutral.
- Long-time overcurrent protection is implemented independently for each phase and for neutral when present.
Setting the Protection
The long-time overcurrent protection settings are:
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Ir: long-time overcurrent protection pickup
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tr: long-time overcurrent protection time delay
They can be set by using the Ir and tr rotary switches on the front face of the TS trip system.
The protection settings and alarm settings can be read by EcoStruxure Power Commission software, and EcoStruxure Power Device app.
The settings are displayed with:
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EcoStruxure Power Commission software
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EcoStruxure Power Device app
Setting the Ir Pickup
The Ir pickup setting value is expressed according to the rated current In.
 WARNING |
|---|
|
HAZARD OF FIRE
Failure to follow these instructions can result in death, serious injury, or equipment
damage.
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Ir pickup = Ir setting x In rated current.
The Ir setting values are: 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, 0.98, 1 and off.
When the current is higher than Isd or Ii, only short-time overcurrent protection and instantaneous protection are operational.
Setting the tr Time Delay
The time delay settings correspond to the tripping times for an overload of 6 x Ir in cold-state conditions.
The table below gives tripping times according to tr time delay.
|
tr setting |
Accuracy |
0.5 s |
1 s |
2 s |
4 s |
8 s |
10 s |
12 s |
16 s |
20 s |
24 s |
|---|---|---|---|---|---|---|---|---|---|---|---|
|
Resulting tripping time at 1.5 x Ir |
0 to -30% |
12.5 s |
25 s |
50 s |
100 s |
200 s |
250 s |
300 s |
400 s |
500 s |
600 s |
|
Resulting tripping time at 6 x Ir |
0 to -20% |
0.5 s1 |
1 s |
2 s |
4 s |
8 s |
10 s |
12 s |
16 s |
20 s |
24 s |
|
Resulting tripping time at 7.2 x Ir |
0 to -20% |
0.36 s2 |
0.69 s |
1.38 s |
2.8 s |
5.5 s |
6.9 s |
8.3 s |
11 s |
13.8 s |
16.6 s |
|
1: Accuracy 0 to -40% 2: Accuracy 0 to -60% |
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Predefined Events
The function generates the following predefined events:
|
Code |
Event |
History |
Severity |
|---|---|---|---|
|
0x6400 (25600) |
|
Trip |
High |
|
0x6200 (25088) |
|
Protection |
Medium |
|
0x0C07 (3079) |
|
Protection |
Medium |
Predefined events cannot be modified by the user. For general information about events, refer to Event Management.
Protection events are generated as follows:
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The start event is generated when the protection picks up.
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The trip event is generated when the circuit breaker tripping voltage release (MITOP) activates.
Recommended Actions
|
Code |
Event |
Recommended actions |
|---|---|---|
|
0x6400 (25600) |
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Check the load and reset the device. |
|
0x6200 (25088) |
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Check the load. |
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0x0C07 (3079) |
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No action required. |
Resetting a Trip Event
For information about resetting the circuit breaker after a trip due to an electrical fault, refer to the relevant document:
- EasyPact MVS1 Circuit Breakers with TS Trip System - User Guide
- EasyPact MVS2 Circuit Breakers with TS Trip System - User Guide