ABB Relion REC670 - Page 221

In order to properly extract the weak subsynchronous signal in presence of the dominating
50Hz signal the SMAI HPAC filter shall be set as given in the following table:
Table 25: Proposed settings for SMAIHPAC
I_HPAC_31_5Hz: SMAIHPAC:1
ConnectionType Ph — N
SetFrequency 31.5
FreqBandWidth 0.0
FilterLength 1.0 s
OverLap 75
Operation On
Now the settings for the multi-purpose overcurrent stage one shall be derived in order to
emulate the existing relay operating characteristic. To achieve exactly the same inverse time
characteristic the programmable IDMT characteristic is used which for multi-purpose
overcurrent stage one, which has the following equation (for more information see Section
“Inverse time characteristics” in the TRM).
[ ]
p
t
A
s B k
i
C
in
æ ö
ç ÷
ç ÷
= + ×
ç ÷
æ ö
-
ç ÷
ç ÷
>
è ø
è ø
EQUATION13000031 V1 EN-US (Equation 109)
In order to adapt to the previous relay characteristic the above equation can be re-written in
the following way:
[ ]
01
1
1
0
so
s
so
t
K
I
s T
I
I
æ ö
ç ÷
ç ÷
= + ×
ç ÷
æ ö
ç ÷
-
ç ÷
ç ÷
è ø
è ø
EQUATION13000032 V1 EN-US
(Equation 110)
Thus if the following rules are followed when multi-purpose overcurrent stage one is set:
•
in >
= I
S0
= 300A
•
35566
118.55
300
so
A
K
I
= = =
•
01
0.64B T= =
•
0.0
C =
•
1.0
p =
•
1.0
k =
then exact replica of the existing relay will be achieved. The following table summarizes all
required settings for the multi-purpose function:
1MRK 511 358-UEN A Section 11
System protection and control
215
Application manual