ABB RET670 Commissioning Manual page 208

Section 11
Testing functionality by secondary injection
202
In the following equations, restrain voltage is the magnitude
of the minimum phase-to-phase voltage in secondary volts.
The set operate value in secondary amperes is calculated according to the
following equations:
First part of the characteristic (Restrain voltage ≤ 25% of UBase):
StartCurr CT sec
IBase
× ×
100 CTprim
IECEQUATION2432 V1 EN-US
Second part of the characteristic (25% of UBase ≤ Restrain voltage ≤
UHighLimit/100*UBase), valid when setting parameter VDepMode = Slope:
StartCurr CT sec VDepFact

 

IBase 1
× ×  × −

 
100 CTprim

 

 UH i i ghLimit 25
( ) VT
−
UBase
× ×
 
100 VTprim

IECEQUATION2433 V1 EN-US
Third part of the characteristic (UHighLimit/100*UBase ≤ Restrain voltage):
StartCurr CT sec
IBase
× ×
100 CTprim
IECEQUATION2434 V1 EN-US
Example (rated secondary current = 1A):
CT ratio
VT ratio
StartCurr
VDepFact
UHighLimit
IBase
A test for each section of the characteristic of the function VRPVOC may be
performed; that may be achieved by applying the following voltages:
First section of the characteristic:
If VDepMode = Slope, the minimum measured phase-to-phase voltage is
lower than 0,25*UBase; if VDepMode = Step, the minimum measured phase-
to-phase voltage is lower than UHighLimit/100*UBase:
• UL1: Ampl = 10 / √3; Angle = 0°
• UL2: Ampl = 10 / √3; Angle = 240°
• UL3: Ampl = 100 / √3; Angle = 120°
Second section of the characteristic only:
If VDepMode = Slope, the minimum measured phase-to-phase voltage is
between 0,25*UBase and UHighLimit/100*UBase:
VDepFact
×
100


100 25


Re strainVoltage U U Base
× − ×

sec 100

10 000/1A
10 kV/100 V
100%
25%
100%
10 000 A
10 kV
Transformer protection RET670 2.2 IEC
1MRK 504 165-UEN A
(Equation 91)


VT sec StartCurr C C T sec
 

IBase
× + × ×
 

VTprim 100 CTprim
 
 

(Equation 93)
Commissioning manual
VDepFact

×

100

(Equation 92)