ABB PR512, Manual

Page: 10 / 44

8
CHARACTERISTICS AND ORDERING CODES
Current transformers
The current transformers (CT) (two or three
according to the protection functions selected)
must have the following characteristics:
– rated secondary current 1 A
– performance 2.5 VA
– precision 5 P 10
– safety factor 15
– thermal performance (Ith) 25 kA (1s - 50 Hz)
– service frequency 50-60 Hz
– for correct ammeter reading, the CT must be
combined with the following rated primary
currents: 40 A, 80 A, 100 A, 150 A, 200 A, 250
A, 600 A, 1250 A.
The rated current of the CT must be adjusted by
means of the Dip Switches on the front of the
relay. For CTs with other rated currents, the
ammeter reading can be taken as a percentage
of the rated value. In this case, preparation for a
100 A CT is set
Overload values
The overload values allowed are as follows:
– 1.5 x In (continuous)
– 6 x In for 30 s
– 25 kA for 1 s.
Earth fault external toroid
The PR512 relay can be used with an external
toroid to detect the earth fault current, as long as
it has the following characteristics:
– rated primary current at customer’s choice
– rated secondary current 1 A
– performance at 1 x In 1 VA
– precision class 3 or higher
– ultimate precision factor at the customer’s
choice according
to the total preci-
sion class required
– service frequency 50-60 Hz
Power supply
The self-supply circuit, through the current trans-
formers, activates the protection and measuring
functions, even in the absence of an auxiliary
power supply, starting from a minimum value of
primary current of 0.2 x In on at least one phase
fitted with CT.
The external toroid (for the protection functions
50N - 51N) does not contribute to the self-supply.
The unit can be fitted with an auxiliary power
supply with 24 Vd.c. rated voltage, should the
protection, measuring and control functions be
required with the primary current less than 0.2 x In.
This power supply is always indispensable for the
control and dialogue functions in the PR512/PD
version.
The auxiliary voltage must be supplied from a
feeder with galvanic insulation.
Characteristics of the auxiliary power supply
– Input voltage 24 Vcc –20%
... 30 Vcc +10%
– Max. ripple ± 5%
– Max. absorbed current PR52/P: 50 mA
PR512/PD: 150 mA
The apparatus remains galvanically insulated by
this power supply by means of an internal DC/DC
converter.
The auxiliary power supply must be made b
means of a static continuity group independent of
or derived from a busbar system on the supply
side of the circuit-breaker.
Opening solenoid
Circuit-breaker tripping takes place by means of
an opening solenoid with demagnetisation which
acts directly on the circuit-breaker operating
mechanism. The solenoid receives the energy
required for operation directly from the PR512
unit, and does not therefore require any auxiliary
power supply.
Protection and trip signals
The releases have optic indicators on the front
and bistable contacts. The detailed description of
these is given in the paragraphs below.