Sympathetic Tripping refers to the phenomenon in Electrical Systems when a protective device in a healthy section of the system operates for a fault in another section of the system.  Sympathetic tripping results in unnecessary loss of power for healthy equipment. 

There are many causes for sympathetic tripping.  The most common reason is undervoltage which occurs across the system when there is a heavy current due to a short-circuit or an earth fault. 

Another reason for sympathetic tripping can be the flow of capacitive currents in the healthy feeders when one of the feeders gets grounded. 

In Transformers and Generators the Differential relay sometimes operates for an overcurrent which is outside its zone.  This is due to the dc component of the earth fault current.

Preventing Sympathetic Tripping   

Sympathetic Tripping can be prevented by designing smaller feeders with the total loads equally balanced across the different feeders

Reducing the fault level can result in lesser currents in the event of faults.  The fault level can be reduced by the use of current limiting reactors which increase the impedance.

Extreme Inverse settings in IDMT relays can also help the relays discriminate between sympathetic overcurrents and genuine faults. 

Increasing fault clearing times in the faulty feeders reduces the duration of the undervoltage across the system. 

Modern Differential relays have an inbuilt dc filter which prevent sympathetic tripping due to dc components during earth faults.

Useful Videos on Power Transformer Testing by OMICRON

Lighting within the home currently accounts for about 8% of energy bills in the UK. Incandescent and tungsten bulbs have been a standard feature of electrical use since the 19th century, but are gradually being phased out in favour of more energy saving options that save consumers money and benefit the environment. A number of different options are available from online electrical wholesalers or high street retailers, from energy saving bulbs to compact fluorescents, LEDs and dimmers that can help to cut costs and generate more efficient energy. Moreover, these bulbs can be combined with a number of simple energy saving practices that can be followed within the home.

Types of Bulbs and their Benefits

Early incandescent and halogen bulbs relied on a tungsten filament, and remain the norm for most homes. Halogen bulbs are more efficient than incandescent forms, but still lag behind energy saving bulbs in terms of efficiency. The UK Government have promoted schemes to gradually phase out the use of older bulbs, while encouraging a switchover to energy saving lighting options. Energy saving bulbs and lights remains fairly expensive compared to older bulbs, but have the benefit of lasting longer, and reduce electricity bills.

A basic energy saving bulb is 5 times brighter than a standard bulb, and uses 80% less power. If used responsibly, some energy saving bulbs can have a 10 year life span. This length is based on using certain bulbs for three hours a day in parts of the home, and can be an ideal solution for rooms that are not used very often. Energy saving bulbs can result in 75-80% energy savings, and use 4 times less of the wattage of standard bulbs.

Other energy saving bulb options include compact fluorescents. These bulbs use an alternative gas charging method to standard bulbs, and use 20 to 25% less electricity. Again, higher costs for initial purchases can be offset by their long lasting potential and greater energy efficiency.

Another option is to invest in LEDs, or light emitting diodes. These represent strips of about 36 to 48 lights, which when installed can generate 50,000 hours of capacity. Representing 50 times as much capacity as a standard incandescent light, small LED arrays also act as a stylish alternative to hanging fittings, bulbs and lamps within rooms, and are particularly recommended for kitchens.

These lights emit less carbon dioxide than standard incandescent lights, and can consequently help conserve energy and the environment. When looking for energy saving bulbs always check for an Energy Saving Trust Recommended label, or an Energy Related A tag. Energy saving bulbs can also be recycled, and form part of the EU’s Waste Electrical and Electronic Equipment Initiative.

Other Tips

As well as investing in energy saving bulbs, you can also follow some simple steps when using lights in the home. The most basic solution remains turning lights off when they are not being used. Moreover, try to use lights for particular roles, with bulbs being turned off when watching a brightly lit television or computer. If reading, a single lamp is more efficient than keeping a whole room’s lights on. Dimmer switches are also useful in this regard for regulating the amount of light in a room, and can result in 4-9% of electricity savings.

About the author
Serena is a copywriter for a leading supplier of energy saving discount electrical supplies at Discount Electrical. In her spare time she writes various other blogs online on numerous other subjects such as automotive, health and the theatre.

Supplies both constant speed and variable speed induction generators

Teco Westinghouse
Manufacturers of induction generators for wind power solutions

Jyoti Ltd
Manufacturers of induction generators

Manufacturers of a wide range of induction generators

Cummins Generator Technologies
Produces generators from the range of 600VA to 20,000 kVA

Manufacturers a wide range of Synchronous Generators

Provides a range of Synchronous Generators from 150 to 1100kVA

Marelli Motori
Manufacturer of Synchronous generators suitable for industrial, marine and hydropower environment and applications

Manufacturers upto 4200 kVA

GE Power
Manufacturers of a wide range of alternators for diverse applications

Leroy Somer
Manufactures alternators upto 20 MW

Meco Instruments
Power, Leakage and Harmonics Analyzer

Extech Instruments
Three Phase Power and Harmonics Analyzer

Power and Harmonics Analyzer

Hand held Power and Harmonics Analyzer

TES Electrical and Electronic Corporation
Harmonics Analyzers

Schaffner Group
Manufacturers both Active and Passive Filters

MTE Corporation
Solutions for both Three phase and single phase applications

Harmonic Filters India
Manufacturers of a wide range of Harmonic Filters

KEB Combline Harmonic Filters
Harmonic Filters for Industrial applications

Tailor made Harmonic Solution incorporation a wide variety of harmonic filters

Manufacturers of EMC filters, line suppression chokes and Harmonic Filters

Shandong Hoteam Technologies Co., Ltd.
Active and Passive Harmonic Filters and reactive power compensation equipment

Claritas India
Suppliers of Tuned and detuned harmonic filters

Enertech UPS
Manufacturers of Active Harmonic Filters

Manufacturers of Basic, Bench level and Performance Oscilloscopes

Extech Instruments
Dual Channel Oscilloscopes from 5 Mhz to 60 MHz

Agilent Technologies
Wide range of hand held, portable and sampling oscilloscopes

Fluke Corporation
Multi Channel Handheld Oscilloscopes (Scopemeters) for a diverse applications

Hart USA
Suppliers of Oscilloscopes of leading Brands

Gaotek Inc.
Hand Held oscilloscopes and PC based oscilloscopes

Digital Storage Oscilloscopes

Rohde & Schwarz.
Oscilloscopes from 500 MHz to 1 and 2 GHz

Fluke Corporation
Wide range of High Precision Power Analyzers

Cole Parmer
Three Phase Analyzers  providing Harmonics Analysis

Medusa Products
Manufacturers of Power Analyzers

Manufacturers of Power Analyzers for both basic and High Precision applications

Extech Instruments
Hand held Power and Harmonics Analyzers

Manufacturers of Power Analyzers and Transformer Testers

Fluke Corporation
Manufacturers a wide range of Multimeters and measuring devices

Multimeter and ClampMeter

Suppliers of Multimeters and Measurement devices

Metex Corporation
Digital Multimeters and Dual Display Multimeter

Clamp Meters and Multimeter

Kusam Electrical
Manufacturers of Multimeters and other Measuring devices

Hart USA
Analog and Digital Multimeters

Pre-owned Test Equipment

Motion Drivetronics Pvt. Ltd.
Manufacturers of synchronous motors, synchronous gear motors, AC synchronous electric motor, AC synchronous gear motor, uni-directional motors and bi-directional synchronous motors.

Shenzhen Power Motor Industries Ltd
Manufacturers of Synchronous generators based in China

Leroy Somer
Manufactureres of Permanent Magnet Synchronous Motors
Manufacturers of a wide range of Synchronous Motors

General Electric
Manufacturers of Synchronous Motors

Suhder Motors
Manufacturers of Permanent Magnet, Reversible and Hysteresis Synchronous Motors based in Taiwan
Manufacturers of Single Phase Motors
deals with a different types of single Phase motors
Suppliers of Single Phase Motors

Motors from .33 hp to 10hp

Precise Power
15 HP to 30 HP Single Phase Motors

China Electric Motors
Manufacturers of a range of single Phase motors

Manufacturers of single Phase motors from 0.065 to 2.2 kW

Electroadda sPA
Single Phase Motors from 0.06 to 4 kW

Provides a range of dc motors from 24 to 1400 kW
Manufacturers of a range of dc motors
Manufacturers of wound field, permanent Magnet dc motors

T-T Electric A/S
Provides DC motors from a range of 20 to 2000kW
Manufactures of Fractional DC motors and Brushless DC motors
Manufacturers of all types of DC motors and Drives
Manufacturers of Brushed and Brushless DC Motors
Manufacturers of permanent magnet, brushless  and frameless motors

Manufacturers of a wide range of voltage Transformers

Prima Transformers
Manufacturers of voltage Transformers of various capacities

Manufacturers of wide range of Voltage Transformers

MEW India
Manufactures Voltage Transformers from 11kV to 33kV

Aya Instruments
Voltage Transformers for both Single and Three phase applications

Voltage Transformers for a range from 10 kV and 35 kV

Baoguang Group Co.
Provide a wide range of indoor and outdoor voltage transformers

RHM International
Manufacturers of Current Transformers and Bushings

Howard Butler Ltd
Manufacturers of a wide range of current transformers such as rectangular current transformers, split core transformers, Core Balance Current Transformers and CTs for Bus bars

Ericon Transformers
Manufacturers of Ring Type, Rectangular Type and Wound Primary Current Transformers

Mahendra Electrical Works
Manufacturers of Ring Type,  Oil Immersed Bushing CT, Outdoor Oil Cooled , Wound Primary current Transformers

Trio Transformers
Manufacturers of Current Transformers, Control Transformers and Line Communicating Chokes

Transformer Factory
Producers of Current transformers of different types and ranges

Ningbo Electric
Manufacturers of Current Transformers

Manufacturers of Generator Protection Relays

Manufacturers of a wide range of relays for Generator protection schemes

Schweitzer Engineering Laboratories
Offers Generator Protection Relays with numerous functions

Vamp Engineering
Manufacturers of Generator Protection Relays

Provide a wide range of relays for Transformer Protection schemes

Selinc Engineering Laboratories
Transformer relay protection with Transformer condition tracking and Thermal Monitoring

Manufacturers of relays for Transformer Protection

Provide a diverse range of protection relays for all electric equipment including power transformers

GE Protection and Control
Manufacturers of different types protection relays

Toshiba - Transmission and Distribution
Numerical Transformer Protection Relay with metering and recording

Relemac Cables
Manufacturers of cables for various automation systems

Basic Wire and Cable
Manufacturer & Supplier of Specialty Wire & Cables, for Industrial Power, Lighting, , Automation, etc

FSC Global
Instrument cables cover for applications such as building management systems and Petrochemical Industries

Shen Tai Electric Industry Ltd
Manufacturers of Shielded and Unshielded Instrumentation Cables

KEI Wires and Cables
Manufacturers of Cables for Process Instrumentation

Hitech Cable Assembly Systems
Providers of custom wire and cable assemblies

Instrumentation Cables
Supplies instrumentation cables of various types such as paired, individual and tried cables

Kflex Cables
Suppliers of Single, Multicore, Flexible Instrumentation Cables

Finolex Cables
1.1KV Aluminium / Copper conductor with PVC & XLPE insulation

Nu Core
Flexible Power Cables

Kaydour Cables
Manufacturers of Power and Control Cables

RPG Cables
XLPE cables from 66 V to 132 kV in India

Delton Cables
L.V.   XLPE  Insulated or Unarmoured or Round Wire/Flat Wire Strip Armoured Power Cables

Gallant and Wein
Manufacturers of all types of Cables

Provides a wide range of Circuit breakers fo different ratings and types

Manufacturers Circuit breakers upto 800kV

General Electric
Circuit Breakers, Motor Circuit Breaker and Arc Fault Circuit Interruptor

Hyosung Power and Industrial Systems
Manufacturers of Circuitbreakers, Reactors and Transformers

High Voltage AE Power Systems
Manufacturers of SF6 and nonSF6 breakers

Bharat Heavy Electricals Limited
Leading Manufacturer of Switchgear and Electric Machines

BeimCo FRP Products
Discharge and Operating Rods

Pactil Transformers
Manufacturers of Discharge rods based on specifications

Transpower Switchgear Industries
Manufacturers of Discharge and Operating Rods

Arc Insulations
Telescopic Operating and Discharge rods

Danke Power
Isolators, Air Break Switches, Drop out Fuses and Terminal Connectors

Transpower India
Manufacturers of Fuses, Air break Switches, Cable Trays

Pedersen Power Products
Suppliers of MetalClad Switchgear and Bus ducts

Suppliers of a range of HV and LV Switchgear

Greiner GmBH
MV Switchgear manufacturers

Siemens Switchgear
International Manufacturers of Circuit Breakers and other Switchgear

ABB Switchgear
Gas Insulated and Air insulated Switchgear

General Electric
Manufacturers of Air Insulated, Gas Insulated Switchgear for MV and LV applications

Manufacturers of Autotransformers for different applications

VoltAmp Transformers
Manufacturers of Transformers, Instrument Transformers and AutoTransformers

Todd Systems
Manufacturers of a range of stepup, stepdown and reducer Autotransformers

LC Magnetics
Suppliers of Autotransformers upto 500 kVA for both single phase and three phase applications.

Lenco Electronics
Autotransformers from 100VA to 5000VA

Crompton Greaves Global
Manufacturers of Autotransformers and Transformers

Siemens Energy
Manufacturers of a wide range of Auto Transformers

Stepup Electricals
Manufacturers of a wide range Autotransformers

Manumag S.L.
Single phase and Three phase AutoTransformers

Variacco Electrical
Manufacturers of Variable AutoTransformers

Schaffer GmBH
Isolation Transformers for PCBs up to 60VA  for screw fixture.

Victron Energy
Isolation Transformers 2000VA / 3600VA / 7000VA

Guangzhou Yongxiang Electrical Appliance Factory
Manufacturers of single and three phase isolation transformers

Knel Control
Manufacturers of Shielded Isolation Transformers for three phase application

Pliotron Torroidal Power Products
Manufactures isolation Transformers for Medical application

Isolation Transformers for Marine applications

Manufactures single phase isolation transformers up to 2 kVA and three phase isolation transformers up to 9 kVA

General Electric
Supplies a wide range of isolation transformers

Capacitor Trip modules are used in breaker circuits to provide a source of back up power for trip operations in the event of the failure of the breaker control supply.  The capacitor Trip device is usually used in switchgear systems which use an AC control supply. 

If the control supply of a breaker panel fails during operation, the operator will not be able to operate the breakers from a remote location.  This would also compromise the protection scheme as the breaker will not trip even if a command is sent by a protection relay. 

The capacitor trip module consists of a capacitor which stores charge.  This charge is enough to trip the breaker for a certain number of times, say 5 times.  This ensures that the breaker can trip even if the control supply fails during operation.  Capacitor Trip modules are available for both AC and DC control systems. 

Grounding Transformers are used in Ungrounded systems to provide a earth point.  Grounding Transformers are classified into two types

1) Zig Zag Transformers and

2) The Star-Delta Grounding Transformer with secondary unloaded.

We had looked at the Zig-zag Transformer in an earlier Post (Click here). 

Let us now look at the Star-Delta Grounding Transformer

The Star-delta grounding Transformer has a primary which is star connected and a delta secondary.  The phases of the star primary are connected to the busbar while the neutral is grounded.  The secondary of the transformer which is delta connected is usually left unloaded, though it can also be used to supply power.  The delta serves to provide a return flux path for unbalanced loads.  

During an earth fault, the zero sequence currents can flow through the grounded neutral of the transformer.  If the current is to be limited, a resistor can be added in series to the neutral of the transformer primary.