Ground-Fault Protection (G or ANSI 50N-TD/51N)
Presentation
Ground-fault protection provides protection against phase-to-ground fault, which is more sensitive than protection based on phase current only. It is generally used in TN-S systems but could also be used in other earthing systems.
Ground-fault protection is based either on the summation of the phases and neutral current or on the signal delivered by an external sensor, source ground return (SGR) current transformer through the MDGF module.
| NOTICE |
|---|
|
HAZARD OF EQUIPMENT DAMAGE
With MicroLogic Active control unit for IEC standard, when using source ground
return (SGR) with MDGF module:
Failure to follow these instructions can result in equipment damage.
|
Availability
Ground-fault protection is available on:
-
MicroLogic Active 6.0 control units for IEC standard
-
3-pole and 4-pole circuit breakers
External sensors can be used:
-
External Neutral Current Transformer (ENCT): measurement of the current on neutral. For information about the installation of ENCT, consult the instruction sheet on the Schneider Electric website: NHA14388.
-
Source ground return (SGR) protection: including ground-fault protection and an SGR sensor installed around the connection of the transformer neutral point to ground. For information about the installation of the SGR sensor, consult the instruction sheet on the Schneider Electric website: NHA92405.
WARNINGHAZARD OF GROUND-FAULT PROTECTION LOSS AND INSULATION LOSSUse only the MDGF summing module LV848891SP when using the SGR external sensor for source ground return protection with a MicroLogic Active 6.0 control unit.Failure to follow these instructions can result in death, serious injury, or equipment damage.
Ground-fault protection is powered by the current flowing through the internal current transformers of the circuit breaker and it does not require an additional external power supply.
Operating Principle
The ground-fault current is calculated or measured according to the circuit breaker configuration, as shown in the following table.
|
Circuit breaker configuration |
Ig ground-fault current |
|---|---|
|
3P |
Ig = I1 + I2 + I3 |
|
4P |
Ig = I1 + I2 + I3 + IN |
|
3P + ENCT |
Ig = I1 + I2 + I3 + IN (ENCT) |
|
3P or 4P + SGR |
Ig = ISGR |
 |
The ground-fault protection threshold Ig sets the level of ground-fault current at which the circuit breaker trips when reaching the ground-fault protection time delay tg. The time delay tg sets the length of time during which the circuit breaker carries a ground-fault within the ground-fault protection threshold Ig range. The time delay tg can be adjusted to:
|
Ground-fault protection is based on the true RMS current of phases and neutral, up to harmonic 15.
In order to trip on an intermittent electrical fault, the control unit accumulates the intermittent currents in the ground-fault tripping range that do not last long enough to trigger a trip. This accumulation leads to shorter tripping times than those set.
Setting the Protection
Ground-fault protection can be enabled or disabled with EcoStruxure Power Commission software.
The ground-fault protection settings are:
-
Ig: ground-fault protection threshold
-
tg: ground-fault protection time delay
-
I²t (tg): ground-fault protection curve (I²t ON or I²t OFF)
They can be set as follows:
-
On the MicroLogic Active pin code-protected display screen, by pressing the Protection Settings button, and selecting the G (ground-fault protection) area. See Protection Setting Procedure.
-
With EcoStruxure Power Commission software (password-protected)
-
With EcoStruxure Power Device app (password-protected)
Two modes of configuring the protection settings are available:
-
Quick setting mode is used to configure quick protection settings
-
Fine adjustment mode is used to configure fine protection settings
Quick Protection Settings
Quick protection settings are available:
-
On the MicroLogic Active HMI
-
With EcoStruxure Power Device app
Ig setting for MicroLogic Active 6.0 IEC standard
|
Setting |
Unit |
Values |
Factory setting |
Accuracy |
|---|---|---|---|---|
|
Ig for In ≤ 400 A |
A |
(0.3 / 0.4 / 0.5 / 0.6 / 0.7 / 0.8 / 0.9 / 1) x In |
0.3 x In |
+/– 10% |
|
Ig for In > 400 A, excluding 1,250 A |
A |
(0.2 / 0.3 / 0.4 / 0.5 / 0.6 / 0.7 / 0.8 / 0.9 / 1) x In |
0.2 x In |
+/– 10% |
|
Ig for In = 1,250 A |
A |
(0.2 / 0.32 / 0.4 / 0.48 / 0.6 / 0.72 / 0.8 / 0.88 / 1) x In |
250 A |
+/– 10% |
tg setting for MicroLogic Active 6.0 IEC standard
|
Setting |
Unit |
Setting Value |
|||||||
|---|---|---|---|---|---|---|---|---|---|
|
tg with I²t OFF |
s |
0 |
0.1 |
0.2 |
0.3 |
0.4 |
0.6 |
0.8 |
1.0 |
|
tg with I²t ON |
s |
– |
0.1 |
0.2 |
0.3 |
0.4 |
0.6 |
0.8 |
1.0 |
|
Non-tripping time |
s |
> 0.02 |
> 0.08 |
> 0.14 |
> 0.23 |
> 0.36 |
0.55 |
0.71 |
0.9 |
|
Maximum breaking time |
s |
< 0.08 |
< 0.14 |
< 0.20 |
< 0.32 |
< 0.50 |
0.63 |
0.8 |
1.0 |
The default tg time delay setting value is 0 s with I²t OFF.
Fine Protection Settings
Fine protection settings are available:
-
On the MicroLogic Active HMI
-
With EcoStruxure Power Commission software
-
With EcoStruxure Power Device app
Ig setting for MicroLogic Active 6.0 IEC standard
|
Setting |
Unit |
Range |
Step |
Factory setting |
Accuracy |
|---|---|---|---|---|---|
|
Ig for In ≤ 400 A |
A |
0.3–1 x In |
1 A |
0.3 x In |
+/– 10% |
|
Ig for 400 A <In ≤ 1,000 A |
A |
0.2–1 x In |
1 A |
0.3 x In |
+/– 10% |
|
Ig for In > 1,000 A |
A |
0.2–1 x In |
10 A |
0.3 x In |
+/– 10% |
tg setting for MicroLogic Active 6.0 IEC standard
|
Setting |
Unit |
Setting Value |
|||||||
|---|---|---|---|---|---|---|---|---|---|
|
tg with I²t OFF |
s |
0 |
0.1 |
0.2 |
0.3 |
0.4 |
0.6 |
0.8 |
1.0 |
|
tg with I²t ON |
s |
– |
0.1 |
0.2 |
0.3 |
0.4 |
0.6 |
0.8 |
1.0 |
|
Non-tripping time |
s |
> 0.02 |
> 0.08 |
> 0.14 |
> 0.23 |
> 0.36 |
0.55 |
0.71 |
0.9 |
|
Maximum breaking time |
s |
< 0.08 |
< 0.14 |
< 0.20 |
< 0.32 |
< 0.50 |
0.63 |
0.8 |
1 |
Testing the Protection
Test the operation of ground-fault protection as follows:
|
Step |
Action |
|---|---|
|
1 |
Check that the circuit breaker is closed and the control unit is supplied with power (Ready LED is flashing). |
|
2 |
Use the MicroLogic Active HMI to launch the ground-fault protection test. |
|
3 |
The circuit breaker trips. The Ig test trip event is generated. |
|
4 |
If the circuit breaker does not trip, the Ig test - no trip event is generated. Restart the test. If the circuit breaker does not trip again, contact your Schneider Electric Services representative. |
Zone Selective Interlocking (ZSI)
If ZSI IN is not set to 1 (open circuit between Z3 and Z4 terminals), the maximum breaking time is 0.08 s regardless of the tg setting value.
When ZSI IN is set to 1 and connected to the ZSI OUT of a downstream device (or when ZSI is not used, there is a jumper between the Z3 and Z4 terminals), the tg time delay is used.
The Ig threshold activates ZSI OUT (Z1 and Z2 terminals).
Predefined Events
The function generates the following predefined events:
|
Code |
Event |
History |
Severity |
|---|---|---|---|
|
0x6403 (25603) |
Ground Fault (Ig) trip |
Trip |
High |
|
0x641E (25630) |
Ig test trip |
Trip |
High |
|
0x0C09 (3081) |
Ig protection disabled |
Protection |
Low |
|
0x6203 (25091) |
Ig start |
Protection |
Low |
|
0x142A (5162) |
Ig test launched |
Diagnostic |
Low |
|
0x1413 (5139) |
Ig test - no trip |
Diagnostic |
High |
Predefined events cannot be modified by the user. For general information about events, refer to Event management.
Protection events are generated as follows:
-
The start event is generated when the protection picks up.
-
The trip event is generated when the circuit breaker tripping voltage release (MITOP) activates.
Recommended Actions
|
Code |
Event |
Recommended actions |
|---|---|---|
|
0x6403 (25603) |
Ground Fault (Ig) trip |
Reset the circuit breaker. See Resetting a Trip Event. |
|
0x641E (25630) |
Ig test trip |
Reset the circuit breaker. See Resetting a Trip Event. |
|
0x0C09 (3081) |
Ig protection disabled |
No action required. For information only. |
|
0x6203 (25091) |
Ig start |
No action required. For information only. |
|
0x1413 (5139) |
Ig test - no trip |
Restart the test. If the circuit breaker does not trip again, contact your Schneider Electric Services representative. |
Resetting a Trip Event
For information about resetting the circuit breaker after a trip due to an electrical fault, refer to the relevant document:
-
MasterPacT MTZ1 IEC Circuit Breakers with MicroLogic Active Control Unit - User Guide
-
MasterPacT MTZ2/MTZ3 IEC Circuit Breakers with MicroLogic Active Control Unit - User Guide