ABB Relion 670 Series Applications Manual page 260

Section 12
System protection and control
The following figure shoes typical configuration connections required to utilize this filter in
conjunction with multi-purpose function as non-directional overcurrent protection.
IEC13000179 V1 EN-US
Figure 106: Required ACT configuration
Such overcurrent arrangement can be for example used to achieve the subsynchronous resonance
protection for turbo generators.
12.1.3 Setting guidelines
12.1.3.1 Setting example
A relay type used for generator subsynchronous resonance overcurrent protection shall be
replaced. The relay had inverse time operating characteristic as given with the following formula:
=
t T
op 01
EQUATION13000029 V1 EN-US
Where:
• t is the operating time of the relay
op
• T
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
minimal subsynchronous current trip level was set at I
Solution:
254
It is recommended that the trip time delay of under voltage or under current
functions is set longer than the SMAIHPAC FilterLength to allow time for the
SAMIHPAC outputs to stabilize at startup.
K
+
I
s
is fixed time delay (setting)
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IEC13000179-1-en.vsd
GUID-5A3F67BD-7D48-4734-948C-01DAF9470EF8 v2
01
= 0.64 seconds, K= 35566 Amperes and
=300 Amperes primary.
S0
1MRK 511 401-UUS F
(Equation 109)
Bay control REC670
Application manual