Siemens SIPROTEC 7SJ62 Instruction Manual

Functions
6-277SJ62 Manual
C53000-G1140-C121-1
pickup and delay such that operation of the 50-2 element will coordinate with other
protective equipment in the system.
Below is an example of how a 50-2 relay element might be set to protect a power
transformer in a radial distribution system against high magnitude internal faults:
Example:
Transformer used to supply distribution bus with the following data:
Based on the data above, the following are calculated:
The minimum pickup setting for the 50-2 element can be governed by a single inequal-
ity:
If the pickup of the 50-2 relay element is set according to the inequality above, the 50-
2 element will never pickup for a fault beyond the transformer’s low-side bushings,
even if changing system conditions increase the high side fault MVA. Using the ine-
quality above as a guide, a setting of 10.00 amperes is chosen for the 50-2 element.
At address , a short time delay should be entered to prevent inrush currents from
initiating false trips.
For motor protection, the 50-2 relay element must be set smaller than the smallest
phase-to-phase fault current and larger than the largest motor starting current. Since
the maximum motor starting current is generally on the order of 1.6 times the nominal
motor current, the 50-2 phase element should be set as follows:
The potential increase in starting current caused by overvoltage conditions is already
accounted for by the 1.6 factor. The 50-2 phase element may be set with no delay
since, unlike the transformer, no saturation of the cross reactance occurs in a motor.
If the reverse interlocking principle is used (see Subsection 6.2.1.3), the 50-2 element
can be employed in a high speed bus protection scheme. With a brief safety delay en-
tered at address  (50 ms), the 50-2 element can be blocked for faults beyond the
Base Transformer Rating 16 MVA
Transformer Impedance (Z
TX
)10 %
Nominal High Side Voltage 110 kV
Nominal Low Side Voltage 20 kV
Transformer Connection Delta-Grounded Wye
High Side Fault MVA 1,000 MVA
High Side Current Transformer Ratio 100 A / 1 A
Low Side Current Transformer Ratio 500 A / 1 A
Three-phase high side fault current @ 110kV 5250 A
Three-phase low side fault current @ 20kV 3928 A
Three-phase low side fault current @ 110kV 714 A
Transformer full load current @ 110kV
(I
Base-110kV
)
84 A
Transformer full load current @20kV
(I
Base-20kV
)
462 A
High side current transformer ratio (CTR-HS) 100 A / 1 A
Low side current transformer ratio (CTR-LS) 500 A / 1 A
50-2 Pickup
1
Z
TX
----------
I
Base-110kV
CTR-HS
----------------------------
×>
1,6 I
startup
⋅ 50-2 Pickup I
φφ Min
–
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Siemens SIPROTEC 7SJ62 Specifications

General

Brand	Siemens
Model	SIPROTEC 7SJ62
Category	Relays
Language	English