Test Example 1 - GE T60 Instruction Manual

8.2 DIFFERENTIAL CHARACTERISTIC TEST EXAMPLES
a) DESCRIPTION
TRANSFORMER DATA:
• 20 MVA, 115/12.47 kV, CT (HV) = 200:1, CT (LV) = 1000:1, Y/y0° with a grounded LV neutral
TEST SET CONFIGURATION:
The fault current distribution for an external b-c fault is identical for the HV and LV transformer sides and can be simulated
easily with two current sources. Connect the first current source to the relay Phase "B" and "C" terminals, corresponding to
the HV winding CTs in series, and the second source to the Phase "b" and "c" relay terminals, corresponding to the LV CTs.
Ensure the polarity is correct and the relative phase angles are similar to the shown in the figure; that is, 180° between IB
and IC, 180° between Ib and Ic, 180° between IB and Ib, and 180° between IC and Ic. Follow the magnitudes and angles of
the injected currents from the tables below to ensure the test will be performed correctly
OPERATING CRITERIA:
The differential element operates if the differential current (I
restraint current magnitude (I
est compensated current. Compensation refers to vector and magnitude corrections applied to the currents from the HV
and LV transformer sides.
The tests verify the operation and no-operation response for points from all regions of the percentage differential character-
istic. These tests are:
• Test for zero differential current
• Minimum Pickup
• Slope 1
• The region between Slope 1 and Slope 2
• Slope 2
RELAY CONFIGURATION:
The AC Inputs and Source are configured as follows:
AC INPUTS SETTING
Phase CT Primary
Phase CT Secondary
Ground CT Primary
Ground CT Secondary
TWO WINDING TRANSFORMER CONFIGURATION:
WINDING 1 SETTINGS
8
Source
Rated MVA
Nom Ph-Ph Voltage
Connection
Grounding
Angle WRT
Resistance 3Ph
Application of excessive current (> 3 ´ In) for extended periods damages the relay.
8-4
). The differential current I
r
CT F1 CT M1 SOURCE SETTING
200 1000 Name
1 1 Phase CT
X X Ground CT
X X Phase VT
Aux VT
VALUE WINDING 2 SETTINGS
SRC 1 Source
20 MVA Rated MVA
115 kV Nom Ph-Ph Voltage
Wye Connection
Not within zone Grounding
0° Angle WRT
10.000 ohms Resistance 3Ph
T60 Transformer Protection System
) exceeds the characteristic defined by the relay settings for
d
is the vector sum of the compensated currents, and I
d
SOURCE 1
SRC 1
F1
X
X
X
VALUE PERCENT DIFF
SRC 2 Minimum PKP
20 MVA Slope 1
12.47 kV Breakpoint 1
Wye Breakpoint 2
Within zone Slope 2
0°
10.000 ohms
8 COMMISSIONING

8.2.2 TEST EXAMPLE 1

is the larg-
r
SOURCE 2
SRC 2
M1
X
X
X
VALUE
0.1 pu
15%
2 pu
8 pu
95%
GE Multilin