Application - ABB RELION REX640 Technical Manual

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Protection functions

whole function is blocked and the timers are reset. In the "Block OPERATE output"

mode, the function operates normally but the OPERATE output is not activated.

Application

INTRPTEF is an earth-fault function dedicated to operate in intermittent and

permanent earth faults occurring in distribution and sub-transmission networks. Fault

detection is done from the residual current and residual voltage signals by monitoring

the transients with predefined criteria. As the function has a dedicated purpose for the

fault types, fast detection and clearance of the faults can be achieved.

Intermittent earth fault

Intermittent earth fault is a special type of fault that is encountered especially in

compensated networks with underground cables. A typical reason for this type of fault

is the deterioration of cable insulation either due to mechanical stress or due to

insulation material aging process where water or moisture gradually penetrates the

cable insulation. This eventually reduces the voltage withstand of the insulation,

leading to a series of cable insulation breakdowns. The fault is initiated as the phase-

to-earth voltage exceeds the reduced insulation level of the fault point and mostly

extinguishes itself as the fault current drops to zero for the first time, as shown in

243. As a result, very short transients, that is, rapid changes in the form of

spikes in residual current (Io) and in residual voltage (Uo), can be repeatedly

measured. Typically, the fault resistance in case of an intermittent earth fault is only

Residual current Io and residual voltage Uo

GUID-D70774CD-CF07-4748-ACFF-F16FE3F40FE6 V1 EN

Typical intermittent earth-fault characteristics

1MRS759142 C

Pulse interval

~0.1 ... 5 kA

Technical Manual

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