Example Setting And Calculation - DEMA CPM 310 G User Manual

EXAMPLE SETTING AND CALCULATION

Project: It is required that the protection and alarming system of an oil-immersed type power
transformer with characteristics 2,500 kV∙A, (34.5 / 0.4) kV, 50 Hz is erected, using DEMA CPM 310 G.
Protection current transformers are selected as type 60 A / 5 A, 5 V·A 5P10
configured so that the CB control and position indication is achieved via the relay; additionally, it must
be alarmed by means of an acoustic alarm system if by any reason the relay is out of service. The
power transformer operator should be informed means of an acoustic alarm system, if the power
transformer goes through an alarm state or tripped out of service. The neutral current of the
upstream power transformer is restricted via resistor banks.
Settings: Relay settings will be done following the steps at p.43.
1. To fulfill the requirements of the project, do the cabling according to the application diagram
described at p.190 and given at p.191.
2. Once cabling is done and auxiliary power is supplied to the relay, drive the internal unit of the
relay out. Because the nominal secondary current of protection current transformer is 5 A, dip-
switch settings must remain as the default ON-ON-ON-ON-ON setting (see p.47); check it. After
checking, drive the internal unit inside the case and lock it.
3. The protection current transformer is selected as 60 A / 5 A. Go to the Current Transformer
Settings Menu, set Primary Nominal Phase Current and Primary Nominal Earth Current parameters
to 60 A and Secondary Nominal Phase Current parameter to 5 A and Secondary Nominal Earth
Current parameter to T1-5A (see p.100 – 101).
4. Do the settings below in the Automatic Control Settings Menu:
Input Settings
a. Input 1: Buchholz Alarm.
b. Input 2: Buchholz Trip.
c. Input 3: Thermometer Alarm.
d. Input 4: Thermometer Trip.
e. Input 5: CB Position.
Output Settings
a. Output 3: CB Close
b. Output 6: Trip, Buchholz Alarm, Thermometer Alarm.
No changes are to be made to default settings in Automatic Control Settings Menu. ↺
3 The nominal power of current transformers should be determined according to the calculated
secondary burden. The burden is calculated by adding up the secondary cable and the protection
relay consumption.
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3 . System must be