ABB RELION REB500 Technical Manual page 104

Section 5
Bay protection functions
c-Setting can also be set to RXIDG , in which case the function's inverse characteristic
corresponds to that of the relay type RXIDG.
t [s] = 5.8 - 1.35 LN (I / I
The parameter
Multiplier k1-Setting
The multiplier 'k1-Setting' enables the characteristic to be shifted. This is used for grading a
series of relays along a line to achieve discrimination.
For example, in the case of the "very inverse" characteristic, the constant c = 1 and the factor
k ≤ 13.5. The operating time t is given by the equation
1

t
Assuming a grading time of 0.5 s at 6 times the base current I
each of the relays is given by
k1 = 5 t
For operating times between 0.5 and 2.5 s, this results in the following settings for k1:
t [s]
0.5
1
1.5
2
2,5
The characteristics according to BS 142 are set as follows:
• normal inverse: k1 = 0.14 s
• very inverse: k1 = 13.5 s
• extremely inverse: k1 = 80 s
• long time earth fault: k1 = 120 s
Typical settings
• I -Setting corresponding to load current of the protected unit
B
• IStart 1.1 I
• c-Setting according to desired characteristic for the protected unit
• k -Setting according to the time grading calculation
1
• tmin 0.00
98
)
B
k1-Setting has no influence in this case.
k
1
 
I

  1
 
I
B
k [s]
1
2.5
5
7.5
10
12.5
B
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1MRK 505 406-UEN B
is required, the factor k1 for
B
Bay protection functions REB500
Technical manual