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Introduction

• Circuit Breakers are essential component in the entire High Voltage Portfolio

• Circuit Breaker mainly consist of an interrupting Unit ,Circuit Breaker operating mechanism and linkage

• The mechanism that drive the moving part to close and open the breaker is of particular important as long as the closing and opening achieved through mechanical motion

• The peculiar requirement for circuit barker operation poses particular requirement of the operating mechanism

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• The special requirement is that it will not operate under normal condition.

• But must operate at a very short notice the requirement is raised. It's must move as quickly as possible.

• The requirement of the circuit breaker operating mechanism can be summarized as follows,

A. Close the breaker and keep it in the closed position

B. Open the breaker an keep it in the opened position

• These commands are spontaneously given to the circuit breaker at irregular time without any warning.

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• SF6 puffer interrupters have been successfully introduced in the market more than 40 years ago, followed by the self blast interrupters mid of the 80th.

• By that the operating mechanism energy was significantly reduced by a factor of 3 to 4 compared to a system comprising a puffer interrupter unit.

• Today, up to rated voltages of 170kV and rated short circuit currents of 50kA self blast interrupters are common (mainly with triple pole operation)

• For rated voltages ≥ 245kV and/or high rated short circuit currents of 63/80kA puffer interrupters are still exclusively applied (mainly with single pole operation)

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The necessary Characteristics of Operating Mechanism 1. Closing Operation

• On receipt of the closing signal, circuit breaker must closed filly and remain in the close position.

• The most critical requirement for a circuit

breaker is a case where the closing causes the maximum fault current to the flow

2. Tripping Operation • The CB must open fully from the close position

on receipt of the tripping signal.

• It must interrupt the current of specified value by opening

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3. High Speed Reclosing Operation • Closing immediately following the opening

operation also required for CBs to minimize to time during which there is a voltage in the power system

• When the reclosing time set less than 1 sec it’s called High speed reclosing

• The operating mechanism required for breaker, • To satisfy this operation quick resetting of the

latch and trigger.

• To storage of energy both closing operation and energy may required for tripping operation.

• This is achieved by energy store in the

pressurized fluid or energy store in springs.

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Different Types of operating Mechanisms in Circuit Breakers

• Circuit breaker operating mechanisms are characterized in different technologies

• They Can be divided in to 5 groups,

1) Pneumatic

2) Hydraulic

3) Mechanical Spring

4) Hydro Mechanical Spring

5) Power Electronic (Motor Drive)

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Pneumatic Operating Mechanism

• Those mechanisms were first on the market (all ready in the 60th) when high energy demand for circuit breaker has been required.

• In this technology uses compressed air as the energy sources for closing and tripping the CB.

• This is widely used because compressed air is convenient form of store energy.

• The out put energy can be adjusted the various requirement by changing the size of the driving cylinder

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Parts of Pneumatic Operating Mechanism

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Schematic Drawing of a Pneumatic Operating Mechanism

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• The holding latch hold the breaker in the opening position and at the same time the cylindrical valve, which supply air to the driving cylinder is held the shut position by the engagement of the lever and the latch.

• When the closing signal releases the holding latch which then release pin A, the closing spring is freed, closes the CB and then sustains the breaker in the close position.

• The opening signal frees the trigger and the cylindrical valve is freed to supply air to the driving cylinder, The compressed air supply through the control valve drives the piston to the open position.

• At the end of opening stoke the control valve mechanically closed by the cam which make lever turn in the counter clockwise direction

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Advantages • Inertia is low, even for large outputs

• Energy storage for a large number of duty cycle s can be

readily provide

• The mechanism can have a degree of self regulation as the load increases velocity of the driving piston falls, cylinder pressure increases to achieve a new state of balance Disadvantages

• Intensive maintenance requirements of the compressor

• Noisy operation

• High pressure made the available energy for switching operation very temperature sensitive

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LW23-252 outdoor H.V.A.C dead tank SF6 circuit breaker with pneumatic operating mechanism

Application example of a classical pneumatic operating mechanism (ABB type PKA)

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132KV pneumatic operating mechanism Circuit Breaker at Mallawapitiya Grid ,Kurunagala

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Hydraulic Operating Mechanism

• Pneumatic operating mechanisms were replaced the hydraulic ones

• The energy of pressurized oil stored in a Nitrogen accumulator it’s common to use oil energy both opening and closing operation.

• The hydraulic mechanism is working with a much higher working pressure (around 300 bar) compared to a classical pneumatic operating mechanism.

• The pressure is generated by a hydraulic pump.

• Energy transmission is realized by a wear-free hydraulic system.

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Schematic diagram of hydraulic operating mechanism

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• The spaces on the both side driving pistons can be filled with pressurized oil and the spaces of the right hand side of the piston is permanently connected to the accumulator oil

• The piston is driven towards the right when both sides of the piston are pressurized, because the pressurized surface area is greater than the left hand side than right hand side.

• The piston is drive leftward or rightward by filling or releasing high pressure oil in the left hand space.

• In the opening operation, the fully open position is detected by a pressure detecting port that is pressurized in the full open position of the piston

• The detection of full stokes help to reset the control valve and pushes the holding latch through and auxiliary piston.

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• The closing operation is initiated by the releasing the pressure in the auxiliary piston, which then release the holding latch

• The mechanism that held in the closed position by the oil pressure.

• The high pressure in the oil could be cause some leakage of the joint of the hydraulic circuit components.

• The high pressure components are placed in the low pressure oil tank to minimize the effect of leakage in practical operation.

• Typical for this type of technology is the interconnection of discrete modules by external piping (hydraulic cylinder, nitrogen accumulator, pump, pressure switch)

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Advantages

• Because of High pressure size of driving cylinder and consequently size of mechanism as whole can be less than that of other mechanisms.

• Higher driving energy can be achieved by compact mechanism

Disadvantages

• Frequent maintenance of the hydraulic operating mechanism is required.

• Due to the extreme high gas pressure, the gas tank of the hydraulic operating mechanism has to meet pressure vessel regulation in certain countries.

• switching behavior is temperature sensitiveness.

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Application example of a hydraulic operating mechanism (ABB type HA and HKA)

Hydraulic Mechanism By

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Spring Operating Mechanism

• With the introduction of the self-blast breaker technology interrupters mid of the 80th and the reduced required switching energy, spring operating mechanisms are continuously replacing hydraulic and pneumatic operating mechanisms.

• Therefore today they are widely applied in the sub transmission range < 200 kV and for energy level up to 4kJ for opening. Spring operating mechanisms with more than 4kJ for opening are available as well

• They are applied for rated voltages up to 800kV and puffer interrupter.

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• The mechanical stress on the linkage, which is necessary to transmit the energy stored in the spring to the breaker, was reduced.

• To abolish the kinetic energy after each switching operation, an external damper is required.

• Both, damper and the whole kinematic transmission chain should be periodically checked and maintained to guarantee its proper functionality.

• Since the energy storage takes place in springs, this technology is not sensitive towards temperature changes.

• A mechanical spring mechanism usually consists of two springs, one for open and one for close operation.

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• The closing spring generates the required force to close the circuit breaker and charge the opening spring

• Hence, the mechanical energy needed for the re-opening is always stored in the opening spring when the circuit breaker is in the closed position.

• The opening spring is either mounted in the operating mechanism and/or in the circuit breaker.

Spring charged mechanism Vacuum CB

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Schematic drawing of a Spring operating Mechanism

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• The closing spring charged by rotating the ratchet wheel through a pair of ratchets driven by a motor.

• When the ratchet wheel is driven beyond the dead point the spring gives a torque in the clockwise direction and this torque is sustained by the pin B with the closing holding latch.

• When this engagement is released, the ratchet wheel is free and rotates clock wise together with the closing cam. The rotation of closing cam push the lever counter clockwise

• This motion compress the trip spring and at the end of tripping motion the lever is held by the engagement of pin A and the trip holding latch.

• When the energy of the closing spring fully discharged by the closing operation the charging motor is switched on.

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Spring charged operating mechanism type ML -14- 0

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Operating mechanism connected to a life tank breaker for an energy level of 1-1.5kJ composed by clock springs

Operating mechanism connected to a life tank breaker with higher energy level composed by a set of parallel helical wound cylindrical springs

Video

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Typical Circuit-Breaker Control CIRCUIT (Motor/Spring Operated)

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Hydro-Mechanical Spring Operating Mechanism

• The hydro-mechanical spring operating mechanism is basically a combination of the classical hydraulic operating mechanism and the mechanical spring operating mechanism.

• The main feature is the energy storage in highly reliably disc springs. Operation is controlled by hydraulic valves.

• The energy transmission is realized by hydraulic pistons. The damping of the circuit breaker is integrated in the hydraulic system.

• Due to the low number of moving parts and the operating principle the operating mechanism is almost maintenance free

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• The modular design includes a power-pack without any kind of external hydraulic pipe and a monitoring module for control purpose.

• The main modules of the operating mechanism (complete portfolio) are the charging module, storage module, working module, control module and the monitoring module.

• The low pressure reservoir, the working module, and the disc spring assembly are arranged coaxially to the central axis at 60- degree rotation intervals.

• By means of the three storage pistons, the mechanical energy components of spring force and spring travel are converted to the hydraulic energy components of pressure and volume.

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• The oil medium between the high pressure system and the operating cylinder serves as a flexible linkage with a fast acting control valve positioned in the flow path for closing and opening operations

• The mechanism control and

energy transmission are based on the field proven structural elements of the hydraulic operating technology such as the high pressure hydraulic pump, storage piston, and pilot and changeover valves as well as one operating piston with integrated hydraulic end position damping for both closing and opening operations

Typical hydro-mechanical operating mechanism (type HMB-16), applied for 1100 kV gas insulated switchgear,

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Power electronics based operating mechanism ( Motor Drive)

• One of the most recently-developed operating mechanism is the electrical motor drive.

• Essential Component in motor drive System

1. Motor Unit 2. Converter Unit 3. Control Unit 4. Capacitor Unit 5. Charging Unit 6. I/P and O/P Unit

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Motor Unit

• High Torque Servo motor

• Only moving part in the Motor Drive

• Integrated precision Position “resolver”

• Low mechanical Stress

• Low noise Level

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Converter Unit

• Transmits energy from capacitor Unit to motor Unit

• Simple electronic energy Transmission

• Uses proven industrial power electronics

• Controlled via controlled Unit

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Control Unit • Stores and execute contact

travel program

Interfaces via I/O unit

Controls motor via converter

Checks motor positions via resolver continuously

Feedback control algorithm

• Contact travel program stored in robust EEPROM

• Inherent Monitoring

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Capacitor Unit

• Energy “Buffered” in the capacitor bank

• Capacity without recharging O - 0.3 s – CO

CO – 15 s –CO

• Directly monitored

• Modular installation package

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Charging Unit • Supplies capacitor, control

and I/PO units

• Redundant AC and DC supply inputs Automatic switching to

back up supply

Alarm on supply failure

• Stable continuous power consumption < 60W No high transient loads

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Input and Output Unit

• All signals to/for one interface

• Programmable permissive logic

• Standard DC voltage interface supported

• Plug and play module

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Monitoring

• Motor drive designed with integral active monitoring No extra hardware

needed

All signals from one interface

• Remote online inspection

• Highest reliability for circuit breaker and drive

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Design of the motor drive mechanism

• The PMSM(Permanent Magnate Synchronous Motor) is driven by IPM (Intellect Power Module). This module integrates a three-phase high-speed IGBT converter and matches a drive and protective circuit that is optimizing designed.

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• Two phase currents of the motor are measured by Hall sensors.

• The current signals passing through a filter and some signal translations, get into the control unit as the control signals.

• The rotate speed and the position of the rotor are received by a photoelectric encoder fixed on the rotating shaft. The travel of moving contactors is measured by the travel sensor.

• The computer is connected with the control unit by the Communication Interface. It records and displays the opening and closing operations of the HVCB, and it can also do field debugging to make the motor drive mechanism better meet the requirements of the operations.

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Advantages

• Only one moving part

• Programmed optimum contact travel

• Robust modular system

• Continuous active online monitoring

• Very Quit

• Low stable power requirement Motor drive CB in 145KV

transmission line

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Limitation of today Dive Technology

• Motor charged close springs High short term battery loads

• Trip springs

Fixed Energy

• Electro mechanical latches Precision mechanism

• Mechanical energy transmission

High impacts and dampers

• Hard wired discrete Controls Limited flexibility and intelligence

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Reliability Compression

Failure Rates Un < 200 kV Failure Rates Un > 200 kV

Results of the Cigré statistic (partitioned in minor and major failures) completed by the ABB internal failure statistic of hydro mechanical operating mechanisms (HMB-1/2 for rated voltages <200kV and HMB-4/8 for rated voltages > 200kV)

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Summery of different operating mechanism Technologies

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The main requirements for the future proof operating mechanism • High reliability, robust under all environment conditions

(refer to IEC62271-203) • High switching capability, preferably M2 according to

IEC62271 or even better, means service life of >10.000 CO without maintenance

• Intelligent to meet future grid requirements (Smart Grid)

Therefore, intelligent operating mechanism with self supervision and remote controllability are of importance as well.

• Easy to handle and easy to adapt to new applications,

preferable “plug & play” to avoid longer outages and to avoid high shift costs during the qualification process

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New Technology (Magnetic actuator mechanism)

• Magnetic actuator The heart of the operated mechanism with the switching, latching and release functions • Electronic controller Electronic control of release, operating motion, energy storage and functional reliability. • Capacitor Electrical energy store for a complete auto reclosing cycle. • Sensor Non-contact detection of switch position.

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• Lever shaft The only mechanical component for force transmission from the magnet armature to the vacuum interrupter

Advantages

• Few individual parts

• Simple mechanical sequences

• Extremely high reliability

• High quality standard

• Extremely long life

• Maintenance-free

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