Note that the voltage selection from table 39 is always applicable regardless the actual
external VT connections. The three-phase VT inputs can be connected to IED as either three
phase-to-earth voltages, U
L1
, U
L2
and U
L3
or three phase-to-phase voltages U
L1L2
, U
L2L3
and
U
L3L1
. This information about actual VT connection is entered as a setting parameter for the
pre-processing block, which will then be taken care automatically.
10.1.2.2 Base quantities for CVGAPC function
SEMOD53443-112 v4
The parameter settings for the base quantities, which represent the base (100%) for pickup
levels of all measuring stages shall be entered as setting parameters for every CVGAPC
function.
Base current shall be entered as:
1. rated phase current of the protected object in primary amperes, when the measured
Current Quantity is selected from 1 to 9, as shown in table
38.
2. rated phase current of the protected object in primary amperes multiplied by √3 (1.732 x
Iphase), when the measured Current Quantity is selected from 10 to 15, as shown in table
38.
Base voltage shall be entered as:
1. rated phase-to-earth voltage of the protected object in primary kV, when the measured
Voltage Quantity is selected from 1 to 9, as shown in table 39.
2. rated phase-to-phase voltage of the protected object in primary kV, when the measured
Voltage Quantity is selected from 10 to 15, as shown in table
39.
10.1.2.3 Application possibilities
SEMOD53443-136 v3
Due to its flexibility the general current and voltage protection (CVGAPC) function can be used,
with appropriate settings and configuration in many different applications. Some of possible
examples are given below:
1. Transformer and line applications:
• Underimpedance protection (circular, non-directional characteristic)
• Underimpedance protection (circular mho characteristic)
• Voltage Controlled/Restrained Overcurrent protection
• Phase or Negative/Positive/Zero Sequence (Non-Directional or Directional)
Overcurrent protection
• Phase or phase-to-phase or Negative/Positive/Zero Sequence over/under voltage
protection
• Thermal overload protection
• Open Phase protection
• Unbalance protection
2. Generator protection
• 80-95% Stator earth fault protection (measured or calculated 3Uo)
• Rotor earth fault protection (with external COMBIFLEX RXTTE4 injection unit)
• Underimpedance protection
• Voltage Controlled/Restrained Overcurrent protection
• Turn-to-Turn & Differential Backup protection (directional Negative Sequence.
Overcurrent protection connected to generator HV terminal CTs looking into
generator)
• Stator Overload protection
• Rotor Overload protection
• Loss of Excitation protection (directional positive sequence OC protection)
• Reverse power/Low forward power protection (directional positive sequence OC
protection, 2% sensitivity)
Section 10 1MRK 505 370-UEN D
Multipurpose protection
228 Busbar protection REB670
Application manual
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