ABB REG670 Applications Manual page 473

1MRK 502 071-UEN -
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
• t is the operating time of the relay
op
• T is fixed time delay (setting)
01
• K is a constant (setting)
• I is measured subsynchronous current in primary amperes
S
The existing relay was applied on a large 50Hz turbo generator which had shaft
mechanical resonance frequency at 18.5Hz. The relay settings were T
seconds, K= 35566 Amperes and minimal subsynchronous current trip level was set
at I =300 Amperes primary.
S0
Solution:
First the IED configuration shall be arranged as shown in
for SMAI HPAC filter and multipurpose function shall be derived from existing relay
settings in the following way:
The subsynchronous current frequency is calculated as follows:
= - =
50 Hz 18.5 Hz
f
s
EQUATION13000030 V1 EN
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 50: Proposed settings for SMAIHPAC
I_HPAC_31_5Hz: SMAIHPAC:1
ConnectionType
SetFrequency
FreqBandWidth
FilterLength
OverLap
Operation
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).
æ
ç
A
[ ]
ç
= +
s
t
ç p
æ ö
i
-
C
ç ç ÷
>
in
è ø
è
EQUATION13000031 V1 EN
System protection and control
31.5 Hz
Ph — N
31.5
0.0
1.0 s
75
On
ö
÷
÷
×
B k
÷
÷
ø
Section 13
01
= 0.64
Figure 221. Then the settings
(Equation 258)
(Equation 259)
467