Ground-fault location: The concept

How does a ground-fault location system work?

A ground-fault location system comprises a ground-fault test device and a ground-fault evaluator connected to one or more measuring current transformers. The ISOMETER® of the iso685 series features a built-in ground-fault test device.

Functional sequence

Start ground-fault location by activating the ground-fault test device ISOMETER®.
The ground-fault test device briefly connects the live conductors to ground.
Electronic current limiting, this connection and the ground fault create a closed circuit, in which a test current is determined by the system voltage flows. The test current is limited to a maximum value.
The test current pulse flows from the ground-fault test device via the live conductors, the ground fault Rf and the ground wire (PE conductor) and back to the ground-fault test device.
The test current signal is detected by all measuring current transformers on the circuit and evaluated by EDS ground-fault evaluators.
The fault location can be identified using the assignment between measuring current transformers and circuit.

Automatic ground-fault location/permanently installed systems

The ground-fault monitoring device with built-in ground-fault test device, the ground-fault evaluator and the associated measuring current transformers are components of the installation. Ground-fault location is started automatically by the ground-fault monitoring device.

Manual ground-fault location/portable systems

Manual ground-fault location can be implemented to meet the following requirements:

In addition to permanently installed EDS systems, a portable ground-fault evaluator is used for ground-fault location in secondary outgoing circuits.
If the installation does not have an ground-fault test device, a portable ground-fault test device is used.
If the IT system has been de-energized, a portable ground-fault test device with built-in measuring voltage source is used.

Distinguishing features of main circuit/control circuit

The essential difference in the two applications is in the significantly reduced test current for application in control circuits and/or the response sensitivity.

Characteristics of switching function

All measuring channels are scanned in parallel during ground-fault location.
The max. scanning time is ≤ 10 s.
At the end of this time the relay contact switches the faulty measuring channel concerned.
This switching contact can be used to disconnect the faulty outgoing circuit via a contact element.

Advantages of ground-fault location with the EDS system

Resistance grounding has several advantages over solid grounding:

Optimized maintenance

Ground-fault location without disconnecting the electrical installation
Selective fault location by fast and precise localization of the faulty sub circuit
Centralized indication and operation with LC text display
Reduced maintenance costs

Increased operating reliability

Electrical installations are kept at a high level of availability
Increased productivity because interruptions to operation are avoided
More comfort for customers (service area)

Improved economic efficiency

Time and costs for maintenance are reduced
Weak points in the installation are recognized

Flexible and configurable solutions

Cost-effective construction by modular system components
Measuring current transformers are available in different sizes and shapes (round, rectangular, split core, flexible)

Downloads

Name	Category	Size	Language	Timestamp	D-/B-Number
Electrical safety - Product overview	Product Overviews	4.8 MB	EN	2024/03/0505.03.2024
2020 Guidelines (US)	Technical Information	1.9 MB	EN	2020/06/1515.06.2020