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 86: Required ACT configuration
Such overcurrent arrangement can be for example used to achieve the subsynchronous
resonance protection for turbo generators.
11.1.3 Setting guidelines
11.1.3.1 Setting example
GUID-5A3F67BD-7D48-4734-948C-01DAF9470EF8 v2
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:
EQUATION13000029 V1 EN-US (Equation 107)
Where:
• t
op
is the operating time of the relay
• T
01
is fixed time delay (setting)
• K is a constant (setting)
• I
S
is measured subsynchronous current in primary amperes
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
01
= 0.64 seconds, K= 35566 Amperes
and minimal subsynchronous current trip level was set at I
S0
=300 Amperes primary.
Solution:
First the IED configuration shall be arranged as shown in Figure 86. Then the settings 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 18.5 31.5
s
f Hz Hz Hz= - =
EQUATION13000030 V1 EN-US
(Equation 108)
Section 11 1MRK 511 358-UEN A
System protection and control
214
Application manual
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