ABB Modures LZ92-1 User Manual

- in ungrounded or impedance grounded systems
z
where
u
v
2 I x 1,25
Bmax
(Ohm/Phase)
U lowest phase-to-neutral voltage of the healthy phases for an earth
fault (U = 0.85 x min. rated voltage)
U lowest phase-to-phase rated voltage
v
1.25 safety factor
3.2.2.3 Special underimpedance starting characteristics
10
If it is impossible to satisfactorily set the reach according to Section
3.2.2.2, then the following procedure should be tried.
The influence of the balancing currents must be carefully analysed. For examining
the S phase equations for an R-0 earth fault see Section 3.2.2.2.
The relationship XB/XA may be changed and the forward reach and the backward reach
become different. The origin of the circular characteristic is shifted in the X-
direction.
( . ,,

ABB Modures LZ92-1 Specifications

General

Brand	ABB
Model	Modures LZ92-1
Category	Relays
Language	English