FIELD OF APPLICATION
The present invention relates to an automatic breaker racking unit.
BACKGROUND OF THE INVENTION
De-energization of a power system may lead to additional or increased hazards
including interruption of life-support systems, emergency alarm systems, or
hazardous location ventilation. Hence, as a conventional practice, at almost
every powerhouse manpower performs breaker racking operation 'in' and 'ouf of
an energized bus.
Current OHSA standards for performing safe racking operation on an energized
system requires the use of personal protective equipments (PPE) by the workers
like full-body flash suits and gloves. However, in the event of fault explosions
operators using personal protective equipments remain vulnerable to the
developed intense heat and debris traveling at high-speeds.
Thus for safety reasons an operator should remain out of safe working distance
(arc flash zone) while performing racking operation.
Modern industries use motorized breaker racking devices for performing racking
operations remotely and safely. Such motorized racking devices suffer from the
disadvantage that they fail to protect the breaker health against delivery of excess
abnormal torques to the racking mechanism by the motor.
The PLC based closed loop position control of the drive allows the unit to perform
remote racking operations without the operators intervention and the electrodes can be
placed with precision.
Another advantage is that although new breakers come fitted with such devices,
implementation of such devices into old existing breakers is not feasible because they
demand modification of breakers which leads to taking shutdown of entire bus.
Moreover, any breaker modification may lead to warranty issues with the suppliers.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.1 - A photo view of test setup for Automated Breaker Racking Unit
Fig.2 - Schematic representation of Implementation as per invention
Fig. 3(A) - A photo view of Circuit Breaker
Fig. 3(B) - A photo view of Manual Operation on site as per prior art
Fig. 3(C) - A photo view of Automated Operation at lab as per invention
SUMMARY OF THE INVENTION
The present invention provided with a breaker racking unit with closed loop position
control and torque metering. Torque metering is done indirectly in terms of motor
current for every breaker position.
Use of intelligent closed loop position control with torque metering and torque limiting
with respect stored torque-position profile ensures failsafe and precise breaker
engagement.
Thus the present invention provides an automatic breaker racking unit comprising: a
drive-motor-PLC assembly mounted on a portable trolley; and a motor shaft fitted with
position encoder for coupling with said breaker for eliminating the need for modification
of the breaker for implementing the use of the breaker racking unit.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
In order to-make or to-break the circuit breaker (A7, Fig.3A) first of all the trolley (B,
Fig.l) is set in front of the breaker manually. Then manually engage motor shaft (1A,
Fig.l) with the provided removable shaft (IB, Fig.l) containing flexible coupling (1C,
Fig.l) to the breaker arm (or shaft, ID, Fig.l). Followed with manual checking of
alignment of motor shaft using the sleeve provided with the breaker arm and locking of
wheels (IE, Fig.l) using the wooden wedge once aligned. Connecting one end of the
control and video cables (IF, Fig.l) to the junction box (1G, fig.l) with geared motor
(1H, Fig.l) and camera (II, Fig.l) circuit at trolley (B, Fig.l) and the other end to
CCTV (U, Fig.l) and Controller (IK, Fig.l) behind the mobile panel (A, Fig.l) at
connectors (not visible).
The mobile panel consist nothing but house of a Hooter (1L, Fig.l), CCTV, and
Controller. The Controller consists of memory to store torque-vs-position profile (1M,
Fig.2), intelligence for profile matching and to achieve desired function (IN, Fig.2),
drive (10, Fig.2) to operate the motor as desired, and operator interface (or
connectors, IP, Fig.2) to connect a wired remote hand held terminal (or command unit,
1Q, Fig.l) through command cable (1R, Fig.l). From hand held terminal pressing the
appropriate switch to actuate the drive and rotate the motor clockwise or anticlockwise,
which in turn will raise or lower the electrodes according to the requirement to make
the circuit breaker on or off.
Trolley on the other hand consist nothing but house of a geared motor, incremental
encoder (IS, Fig.l) for position feedback, camera and removable shaft fitted with
wheels. CCTV may be used by the operator remotely located to watch the ongoing
racking operation. Once the breaker is turned off or on as per the desire trolley is
disengaged from the breaker and removed from site and live power may be charged to
the breaker.
Present invention being additional auxiliary equipment eliminates need for breaker
modification or fixing of limit switches etc. inside the breaker for automating the racking
operation.
Intelligent controller limits the motor output torque within programmable percentage
band of torque normally required to rack the breaker on or off under healthy condition.
Such limiting of output torque enhances healthiness of the breaker racking components
by eliminating chances of delivery of excess torque manually by the operator. Moreover,
deviations of motor output torque from the healthy torque (previously stored for
healthy on and off operation as torque-vs-position profile) let the controller detect
abnormal conditions like breaking, slippage, and jamming etc. of the breaker shaft as
well as breaker racking mechanism. Intelligent controller also verifies the engagement
and disengagement torque with known values to ensure that electrodes are engaged or
disengaged properly and detect any abnormal engagement or disengagement.
Controller is programmed automatic execution of counter measures (like automatically
lowering the electrodes and making the breaker off) against detection of such abnormal
conditions, thereby guaranteeing each operation a safe operation (fail-safe-operation).
WE CLAIM :
1. A remotely operable automated breaker racking system for
making or breaking incoming live-power to the outgoing
loads when the power demand alters or a fault arises, the
operation of making (turn-on) or breaking (turn-on)
constituting the activity of racking a circuit breaker (7), the
circuit breaker (7) comprising :- a plurality of power
electrodes (2) with internally configured cavities, a plurality
of load electrodes (3) each disposed at a predetermined gap
(6) from each of said power electrodes (2), the electrodes
(2,3) having ceramic insulators (5), and a breaker arm (4) to
raise or lower the plurality of load electrodes (3),
the system comprising :-
- a portable trolley (B) releasably attachable to the circuit
breaker (7), and acting as a housing for a geared motor,
an incremental encoder (IS) for position feedback, and a
removable shaft with wheels (IB);
- an electrical motor with shaft (1A) manually engageable
with the removable shaft (IB) via a coupling (1C) which
further being coupled to a shaft (ID) of the breaker arm
(4);
- at least one control and video cable (1H), a first end of
which connecting the geared motor (1H), and the
camera (II) via a junction box (1G), a second end of the
cable (1H) being connected to a controller unit (IK);
- a hand-held terminal ( C) remotely disposed to act as an
operator module perably connectable via a command
cable (1Q) to an operator interface (IP); and
- a mobile panel (A) comprising a hooter (IL), a display
(CCTV), and a controller having the operator interface
(IP), means for (1M) to store data representing torque-
vs-position profile, means for (IN) profile matching, and
a drive (10) to control and operate the motor (1H),
the controller being configured to :
- limit the motor output torque within a threshold band of
torque applicable for racking the circuit breaker (7)
under healthy condition by online remote acquisition and
comparison of the output torque with prestored data;
- defect abnormal conditions in the system including those
in the circuit breaker such as breaking, slippage and
jamming on the basis of differential data obtained from
the comparison;
- verify the electrode engagement or disengagement by
maintaining the desired gap (6) of the electrodes (2) on
comparison of the engagement or disengagement torque
value with prestored values including detecting abnormal
engagement or disengagement; and
- automatically execute the preventive activities such as
lowering the electrodes and turning off the circuit
breaker on detection of any abnormal condition.
2. A remotely operable automated breaker racking system
for making or breaking incoming live-power to the
outgoing loads when the power demand alters or a fault
arises, the operation of making (turn-on) or breaking
(turn-on) constituting the activity of racking a circuit
breaker (7), as substantially described and illustrated
herein with reference to the accompanying drawings.

The invention relates to a remotely operable automated breaker racking system
for making or breaking incoming live-power to the outgoing loads when the
power demand alters or a fault arises, the operation of making (turn-on) or
breaking (turn-on) constituting the activity of racking a circuit breaker (7), the
circuit breaker (7) comprising a plurality of power electrodes (2) with internally
configured cavities, a plurality of load electrodes (3) each disposed at a
predetermined gap (6) from each of said power electrodes (2), the electrodes
(2,3) having ceramic insulators (5), and a breaker arm (4) to raise or lower the
plurality of load electrodes (3), the system comprising :- a portable trolley (B)
releasably attachable to the circuit breaker (7), and acting as a housing for a
geared motor, an incremental encoder (IS) for position feed back, and a
removable shaft with wheels (1B); an electrical motor with shaft (1A) manually
engageable with the removable shaft (1B) via a coupling (1C) which further
being coupled to a shaft (1D) of the breaker arm (4); at least one control and
video cable (1H), first end of which connecting the geared motor (1H), and the
camera (1I) via a junction box (1G), a second end of the cable (1H) being
connected to a controller unit (1K); a hand-held terminal ( C) remotely disposed
to act as an operator module perably connectable via a command cable (1Q) to
an operator interface (1P); and a mobile panel (A) comprising a hooter (IL), a
display (CC TV), and a controller having the operator interface (1P), means for
(1M) to store data representing torque-vs-position profile, means for (IN) profile
matching, and a drive (10) to control and operate the motor (1H), the controller
being configured to limit the motor output torque within a threshold band of
torque applicable for racking the circuit breaker (7) under healthy condition by
online remote acquisition and comparison of the output torque with prestored
data;