GE P642 User Manual

function uses the vector sum of the current terminal inputs (on a phase by phase basis) as the input to the
calculation for that winding.
Y
ou associate these current inputs with the system transformer windings with the settings HV CT Terminals, LV CT
Terminals and TV CT Terminals in the SYSTEM CONFIGURATION column as follows:
Setting P642 P643 P645
HV CT Terminals 01
001
011
00001
00011
00111
01011
01111
LV CT Terminals 10
100
110
10000
11000
11100
11010
11110
TV CT Terminals 010
00100
01100
00110
01110
Where the terminals T1 to T5 correspond to the bits in the binary string as follows (1 = in use, 0 = not in use). The bit
order starts with T1 on the right-hand side. For example:
If a CT is assigned to more than one winding, then an alarm is issued (CT Selection Alm). When this DDB signal is
asser
ted, the protection is also blocked.
3.3 PHASE CORRECTION
The device automatically carries out phase correction based on the settings made in the SYSTEM CONFIG column.
For a reverse phase rotation (ACB), the device will automatically form a complementary value for the vector group
ID. You can achieve reverse phase rotation by setting the Phase Sequence setting in the SYSTEM CONFIG column.
The device will then automatically form the complementary value of the set vector group ID by subtracting it from
the number 12 (vector group ID = 12 - set ID).
3.4 RATIO CORRECTION
For transformer differential protection, ratio correction is required. The device automatically calculates the ratio
corr
ection factor for each of the current inputs and displays the calculated matching factors in the SYSTEM
CONFIG column.
As well as the parameters of the power transformer itself, which are defined in the SYSTEM CONFIG column, you
need to set up the CT ratios and polarities. You do this in the CT AND VT RATIOS column with the Polarity, Primary
and Secondary settings for all CTs used.
The device then calculates the ratio correction factors as follows:
Chapter 6 - Transformer Differential Protection P64x
108 P64x-TM-EN-1.3

GE P642 Specifications

General

Brand	GE
Model	P642
Category	Relays
Language	English