PROTECTIVE RELAY TYPE CPR FOR
RUBBER BAG CONSERVATOR
(Model year 2013)
File : CPR
UNCONTROLLED COPY
Rev. 9 dtd 14/05/13
1
General Features
1.1 Characteristics
Power transformer usually prevent contact of mineral oil with air (that contains water due to humidity) using a rubber bag fitted inside conservator tank. If there is an intrusion of air inside the conservator (due
i.e. to a microscopic accident inside rubber bag) this must detected.
The gas detector relay type CPR has been specially developed in order to detect this kind of failure. The
relay is designed in a way that it is able to collect the gas inside himself and give an electric signal as
soon as the gas accumulated reaches a predetermined value. .
1.2 Field of Use
The gas detector relay type CPR may be used with the following characteristic values:
Fluid
pressure in the conservator
working temperature
resistance to vibrations
resistance to shock
2
mineral oil
max 1,2 bar
from - 40°C to + 120°C
up to 3 g on all axes
up to 10 g on all axes
Construction Features, Finish and Accessories
2.1 Construction Features
With reference to drawing and its nomenclature, which also indicates the materials, the device is constructed as follows:

a body made in aluminium alloy equipped with a connecting flange pos. 8 that permit mounting on
conservator by using a flat gasket and 4 screws M10

a cover pos. 9 equipped with a push bottom pos. 3 and a gas release cock pos. 2 that allow checking the contact and draining air from the body.

a terminal box pos. 4, including the trip terminals pos. 6, the earth screw pos. 10 and a cable gland
M25 - M20 for connecting to the external circuits
2.2 Finish
In standard execution, all cast parts are protected by one coat of epoxy primer and one coat of polyurethane paint (total thickness 80 µm), final colour RAL 7030 and screws and washer are in stainless steel;
the protection degree of the device is IP 65. Therefore the device is suitable for outdoor installation in
tropical climate and with industrial pollution.
3
Wiring Diagrams and Contact Performance
3.1 Wiring diagrams
The relay is equipped with one magnetic contact, reed type, that operate when gas inside relay reaches
the preset value. Available wiring diagrams are :
 Wiring diagram ME : 1 normally open contact
 Wiring diagram MT : 1 change-over open contact
3.2 Contact's Performance
3.2.1
Normally open contacts(N/O)
Shock resistance: 50 g for 11 millisecond without false operation
Vibration resistance: min 6 g with a frequency range between 3 and 35 Hz without false operation
Insulation resistance: 1000 mega ohms at 20°Cminimum
Operate time: 3 milliseconds
Release time: 5 milliseconds
Life expectancy: 10 millions operations
File : CPR
UNCONTROLLED COPY
Rev. 9 dtd 14/05/13
Max D.C. resistive load (W): 250
Max A.C. resistive load (VA): 400 at 50 Hz
Max D.C. inductive load (W): 250 (the contact can break 1A at 250 V.D.C. with L/R=40 millisecond.)
Max A.C. inductive load (VA): 400 at 50 Hz
Constant current (A): 3
Max switching voltage (Vrms): 250
Min switching voltage (V): 24
Dielectric strength (Vrms): 800
Max contact resistance (MΩ): 500
3.2.2
4
Change-over contacts (SPDT)
Max D.C. resistive load (W): 130
Max A.C. resistive load (VA): 200 at 50 Hz
Max D.C. inductive load (W): 130 (the contact can break 1A at 110 V.D.C. with L/R=40 millisecond.)
Max A.C. inductive load (VA): 250 at 50 Hz
Constant current (A): 1
Max switching voltage (Vrms): 250
Min switching voltage (V): 24
Dielectric strength (Vrms): 800
Operation
The protective relay CPR operate as follows:

When the atmospheric air is intruded inside the transformer due to rubber bag failure (break or gasket failure) or to microscopic accident it will be collected inside the relay and will cause rotation of
float inside the relay (rotation of float and quantity of gas can be detected from inspection window); a
permanent magnet rigidly connected to the float operates the reed contact.
5
Mounting, Adjustment and Maintenance
5.1 Mounting
The protective relay CPR has to be mounted on the top of conservator (see mounting sketch) using 4
screws and nuts M10. Tightening is obtained using a flat gasket made in NBR.
After mounting and before setting to work, air inside body have to be removed by opening gas release
cock pos. 2.
Circuit can now be tested by pressing push bottom pos. 3.
5.2 Maintenance
The protective relay CPR do not need periodic maintenance; however it is advisable to check regularly
the electric contact and the freely movement of float; this test can be made easily y by pressing the push
button 3.
6
Order Specifications
When ordering it is necessary to indicate
 Size:
CPR 3 : operating volume 400 ± 50 cm³


Wiring diagram (ME or MT)
Special requirements
Example :
To order n r 1 protective relay CPR 3 with 1 magnetic contact
please indicate the following:
Nr 1 relay CPR-ME 3
File : CPR
UNCONTROLLED COPY
Rev. 9 dtd 14/05/13