Calculating General Settings - ABB REC650 Applications Manual

1MRK 511 286-UUS A
3.1.5.1
3.1.5.2
Application manual
faults, fault points and switching states in the network. Although it is possible to make
manual calculations of the different faults it is recommended to use computer based fault
calculations.
The following principle for the phase overcurrent protection is proposed:
• Step 1 serves as the main protection for the 22 kV busbar. This step has a short delay
and also has blocking input from the phase overcurrent protections of the 22 kV
feeders. This is a way to achieve a fast trip of 22 kV busbar short circuits while the
selectivity is realized by means of the blocking from the feeder protections.
• Step 4 is used as back-up short circuit protection for the 22 kV feeders as far as
possible. The time delay principle is chosen according to network praxis, in this case
inverse time characteristics using IEC Normal inverse. As the step shall have an
inverse time characteristic the step 4 function is used.
An inverse time characteristics is not available for step 2 and 3.

Calculating general settings

1. Set GlobalBaseSel to 2
The settings are made in primary values. These values are given in the base settings
in Global base 2.
2. Set directional mode
2.1. Set DirModeSel1 to Non-directional
2.2. Set DirModeSel4 to Non-directional
The function shall be non-directional.
3. Set Characterist1 to IEC Def.Time
Step 1 shall have definite time delay
4. Set Characterist4 to IEC Norm.inv
Step 4: For the choice of the time delayed characteristic IEC Normal inverse is used
in this network.
Calculating settings for step 1
1. Set Pickup1 to 500 % of IBase
The requirement is that step 1 shall detect all short circuits on the 22 kV busbar. The
external network has a maximum source impedance of Z
This impedance is transformed to 22 kV level:
Section 3
REC650 setting examples
= j10 Ω (145 kV level).
sc
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