Setting Guidelines - ABB REC670 Applications Manual

1MRK 511 401-UUS A
12.1.3
12.1.3.1
Bay control REC670 2.2 ANSI
Application manual

Setting guidelines

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:
K
= +
t T
op 01
I
s
EQUATION13000029 V1 EN-US
Where:
• 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-US
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 30: Proposed settings for SMAIHPAC
I_HPAC_31_5Hz: SMAIHPAC:1
ConnectionType
SetFrequency
Table continues on next page
System protection and control
31.5 Hz
Ph — N
31.5
Section 12
GUID-5A3F67BD-7D48-4734-948C-01DAF9470EF8 v2
(Equation 104)
01
= 0.64
Figure 102. Then the settings
(Equation 105)
289