GE Multilin G650, Manual

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9-2 G650 Generator Protection & Control System GEK-113285A
9.2 GENERAL CONSIDERATIONS ON THE POWER SUPPLY NETWORK 9 COMMISSIONING
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9.2GENERAL CONSIDERATIONS ON THE POWER SUPPLY NETWORK
All devices running on AC current are affected by frequency. As a non-sine wave is the result of a fundamental wave plus a
series of harmonics from this fundamental wave, we can infer that devices running on AC current are influenced by the
applied waveform.
For a correct testing of relays running on AC current, it is fundamental to use a current and/or voltage senoidal waveform.
The pureness of a senoidal wave (lack of harmonics) cannot be expressed specifically for a specific relay. However, any
relay incorporating sintonized circuits, R-L and R-C circuits, will be affected by non-senoidal waveforms, as in the case of
G650.
These relays respond to the voltage waveform in a different way to the majority of AC current voltmeters. If the power
supply network used for the testing contains wide harmonics, the voltmeter and relay responses will be different.
Relays have been calibrated in factory using a Network of 50 or 60 Hz with a minimum harmonic content. When the relay is
tested, a power supply network with no harmonics in its waveform must be used.
The ammeters and chronometers used for testing the pickup current and relay operation time must be calibrated and their
accuracy must be better than the relay’s. The power supply used in the tests must remain stable, mainly in the levels near
the operation thresholds.
It is important to point out that the accuracy with which the test is performed depends on the network and on the
instruments used. Functional tests performed with unsuitable power supply network and instruments are useful to check
that the relay operates properly and therefore its operating characteristics are verified in an approximate manner. However,
if the relay would be calibrated in these conditions, its operational characteristics would be outside the tolerance range
values.
The following sections detail the list of tests for verifying the complete relay functionality.