GE G30 - Page 329

GE Multilin G30 Generator Protection System 5-189
5 SETTINGS 5.6 GROUPED ELEMENTS
5
The split phase element allows a separate pickup setting to be applied for each phase. Additionally, the pickup can be
biased by the load current (slope characteristic). Two modes of operation are supported (over and over-under).
Figure 5–76: SPLIT PHASE PROTECTION FOR 2 CTS
Figure 5–77: SPLIT PHASE PROTECTION FOR 1 CT
The split phase element principle of operation is as follows. First, define the following parameters:
I
split
: split-phase current, I
load
: load current, pickup: pickup setting, min_load: minimum load supervision setting
Then, the expected value of the steady state unbalance (defined as bias current) is expressed as follows:
(EQ 5.44)
where:
(EQ 5.45)
and offset is the split phase current at no-load. In “Over” mode, the element will pickup if:
(EQ 5.46)
In “Over-under”, mode, the element will pickup if:
830728A1.CDR
Split Phase
Source
Load
Source
830727A1.CDR
Split Phase
Source
Load
Source
I
bias
slope I
load
× offset+=
slope
I
split
I
load
-----------
Load CT Primary
Load CT Secondary
-----------------------------------------------------
Split Phase CT Secondary
Split Phase CT Primary
----------------------------------------------------------------------
××=
I
split
I
bias
– pickup>() and I
load
min_load≥()