Insulation fault location: The concept

How does an insulation fault location system work?

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

Functional sequence

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

Automatic insulation fault location/permanently installed systems

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

Takt der Prüfstromimpulse des EDS-Systems

Manual insulation fault location/portable systems

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

In addition to permanently installed EDS systems, a portable insulation fault evaluator is used for insulation fault location in secondary outgoing circuits.
If the installation does not have an insulation fault test device, a portable insulation fault test device is used.
If the IT system has been deenergised, a portable insulation 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 insulation 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 insulation fault location with the EDS system

Optimised maintenance

Insulation fault location without disconnecting the electrical installation
Selective fault location by fast and precise localisation of the faulty sub circuit
Centralised indication and operation with LC text display
Reduced maintenance costs

Improved economic efficiency

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

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)

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)

Types of distribution systems for power supply
Advantages of the IT system
Insulation monitoring: The concept
Insulation fault location in coupled systems
Ungrounded system: Application examples
Control circuits as an IT system
Insulation resistance - testing, measuring, monitoring
IT systems as reflected in the standards
Preventive fire protection in building installation
Insulation monitoring devices for safety in the IT system
Insulation fault location during operation
IT system: Unearthed systems for maximum availability

Downloads

Name	Category	Size	Language	Timestamp
Product Overview ISOMETER®/ISOSCAN®	Product Overviews	5.3 MB	EN	2024/02/1616.02.2024
Why the IT System is Often the Best Choice for Power Supply Systems of All Types	Technical article	3.0 MB	EN	2019/07/1111.07.2019
Initial and Periodic Verification of IT Systems	Technical article	621.5 KB	EN	2020/03/0202.03.2020
High Availability for Reliable Operation in Waste Water Treatment Facilities	Technical article	601.8 KB	EN	2019/05/1313.05.2019
IT System Ensures Electrical Safety at the Munich Airport	Technical article	284.0 KB	EN	2019/05/1313.05.2019
The Stone Age Meets Modern Network Protection Technology	Technical article	338.5 KB	EN	2019/05/1313.05.2019
The Largest Photovoltaic System in Latin America	Technical article	447.8 KB	EN	2019/05/1313.05.2019

Products

Insulation monitoring

ISOMETER® iso685…

Insulation monitoring device for inverter applications and large industrial plants

Details