Avoiding the Non-Detection Zone of Passive Loss-of-Mains (Islanding) Relays for Synchronous Generation by Using Low Bandwidth Control Loops and Controlled Reactive Power Mismatches

Generation connected to electrical distribution systems requires reliable and timely detection of loss-of-mains (islanding). Passive loss-of-mains detection relays typically use measurements of parameters such as frequency, phase, and the magnitudes of voltage and current. If a part of the power net...

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Bibliographic Details
Published in:IEEE transactions on smart grid 2014-03, Vol.5 (2), p.602-611
Main Authors: Roscoe, Andrew J., Burt, Graeme M., Bright, Chris G.
Format: Article
Language:English
Subjects:
AC generator excitation
AC generators
Electric utilities
Electricity generation
Frequency measurement
Generators
islanding
Load modeling
loss-of-mains
power generation
power system control
power system protection
power system security
power systems
protective relaying
Reactive power
Relays
Resonant frequency
Voltage measurement
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Summary:Generation connected to electrical distribution systems requires reliable and timely detection of loss-of-mains (islanding). Passive loss-of-mains detection relays typically use measurements of parameters such as frequency, phase, and the magnitudes of voltage and current. If a part of the power network becomes islanded and there is a very close match between generation and demand of both active and reactive power, there is a risk that the relay will not be able to detect the loss-of-mains (LOM) event quickly, or perhaps at all. This is the "non-detection zone" or NDZ. This paper proposes a combination of 2 generator control techniques which allow the NDZ to be avoided even when the generator has significant inertia. Firstly, the natural instability (when islanded) of a grid-connected control scheme consisting of integral and droop controls is recognized and exploited. Secondly, a simple strategy is added which makes occasional small, steady-state adjustments to the reactive power output of the generator. The scheme has been tested in the laboratory and shows that the 2 second detection time required by IEEE 1547 can be achieved, even when an exact match of active power generation and demand is initially configured, and the generator has a significant inertia.
ISSN:1949-3053
1949-3061
DOI:10.1109/TSG.2013.2279016