Page 142 - Practical Power System and Protective Relays Commissioning

Chapter 13

Fault Recorders in Substations

and Power Stations

13.1 INTRODUCTION
In the past there was a need to have a separate fault recorder in substations
and at power stations. In some cases there is now a recorder included in the
new numerical protection relays. However, there is still a need for a separate
fault recorder when we need a detailed information for prefault, fault, and
postfault conditions. Retaining this information requires a large computer
memory, which is only found in separate units.
The inputs for these fault recorder units comes from the voltage trans-
former and the current transformer. The data shows the analog signals Vr,
Vy, Vb, Ir, Iy, and Ib. It also shows the operation of the protection relays
and tripping relays.
Another device available is the sequence of event recorder which shows
the time of operation of substation components such as as circuit breakers
and disconnect switches.
All these devices are very important in analyzing faults within a power
system and to predict any faults that may occur with the system.
For any event in the fault recorder there are three important time sequences:
Prefault time duration
Fault time duration
Postfault time duration
A fault recorder unit can be used to adjust these times, should they occur,
and there is also a setting for which digital channels trigger the recording
process.
A fault recorder consists of the following units:
Data acquisition units that have inputs from the current transformer, volt-
age transformer, analog channels, and digital channels.
Restitution unit which collect the information from data acquisition units.
Local computer unit.
Local printer.
Fig. 13.1 shows a setup for a fault recorder unit.

Practical Power System and Protective Relays Commissioning.
DOI: https://doi.org/10.1016/B978-0-12-816858-5.00013-7 141
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