Abstract
Issues of increase of consumer power supply reliability by prevention of protection device false operation and unreasonable tripping of the protected network element at malfunction of measuring voltage transformer secondary circuits are considered. Options for implementation in relay protection microprocessor terminals of advanced blocking algorithms in case of voltage circuits fault are proposed.
Highlights
Reliability, along with speed of response, sensitivity and selectivity, is the main characteristic of relay protection devices
Unreliable relay protection device itself becomes a source of accidents, and false triggering of protective relays lead to unreasonable network tripping which leads to economic losses due to production or technological failures
Damages to the voltage transformer circuits leads to a false triggering of relay protection devices, which use the voltage signal
Summary
Reliability, along with speed of response, sensitivity and selectivity, is the main characteristic of relay protection devices. Damages to the voltage transformer circuits leads to a false triggering of relay protection devices, which use the voltage signal. The very moment of damage and subsequent triggering of the circuit breakers or fuses lead to distortion of voltage signal and improper operation by relay protection devices. A fact of voltage circuits’ damage should be detected by voltage circuit lock function which sends a fault signal and blocks operation of relay protection device which use information from the voltage measuring elements. Relay protection devices can be connected to secondary windings of voltage transformers worked in the network with isolated neutral in several ways (Fig. 1) depending on the scheme of secondary voltage circuits at the substation and necessity of information about the signal parameters (Table 1). Calculation of zero sequence value and measurement of phase-to-ground voltages are possible when the terminal is connected to output N of Y-circuits (Fig. 1, b, d). To measure zero sequence voltage, H and K circuits are used as open delta winding terminals
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