Application - ABB 615 series Technical Manual

1MAC059074-MB A
4.2.8.5
615 series ANSI
Technical Manual

Application

67YN provides selective directional ground-fault protection for high-impedance
grounded networks, that is, for compensated, ungrounded and high resistance grounded
systems. It can be applied for the ground-fault protection of overhead lines and
underground cables.
The operation of 67YN is based on multi-frequency neutral admittance measurement
utilizing cumulative phasor summing technique. This concept provides extremely secure,
dependable and selective ground-fault protection also in cases where the residual
quantities are highly distorted and contain non-fundamental frequency components.
67YN is well-suited for compensated networks where measurement signals may have
such characteristics, for example, during intermittent ground faults.
67YN is capable of operating with both low ohmic and higher ohmic ground faults, where
the sensitivity limit is defined with residual overvoltage condition. This allows ground
faults with several kilohms of fault resistance to be detected in a symmetrical system. The
sensitivity that can be achieved is comparable with traditional fundamental frequency
based methods such as the IoCos/IoSin (67/51N, 67/50N), Watt/Varmetric (32N) and
neutral admittance (21YN).
67YN is capable of detecting faults with dominantly fundamental frequency content as
well as transient, intermittent or restriking ground faults. 67YN can be used as an
alternative solution to transient or intermittent function 67NIEF.
67YN supports Fault direction indication in operate and non-operate direction which may
be utilized during fault location process. The inbuilt transient detector can be used to
identify restriking or intermittent ground faults, and discriminate them from permanent or
continuous ground faults.
The direction of 67YN can be set as forward or reverse. The operation characteristic is
defined by a tilted operation sector, which is universally valid both in ungrounded and
compensated networks. The tilt of the operation sector should be selected based on the
measurement errors of the applied residual current and voltage measurement
transformers.
The operating time characteristic is according to the definite time (DT).
The function contains a blocking functionality to block function outputs, timers or the
function itself.
67YN supports both tripping and alarming mode of operation. For alarming ground-fault
protection application, the function contains a dedicated operation mode.
67YN provides reliability and sensitivity of protection with a single function. This enables
simpler implementation of protection schemes as separate fault type dedicated ground-
fault functions and coordination between them are not necessarily required. Other
Section 4
Protection functions
457