Electricalreads

Ohm’s Law is the heart of electrical engineering, It is one of the best principle of Electrical circuit. Ohms Law is the basic principle used and all other rules are the based on it. Ohm’s Law: Voltage equals current multiplied by resistance; it is shown in above Figure. The basic fact is that resistance creates/impedes the current flow. So, this Impedance creates the Voltage drop across the resistor that is proportional to current flowing through it. Now, we have used the word Impedance, so Resistance is one of the quantity of Impedance. Two other quantities Inductor and capacitor are also part of the Impedance. Depending on the frequency of the power supply Inductor and capacitor also works as Resistor. Impedance is nothing but a resistance but keep in mind it causes delay in phase of the signal. So, Ohm’s Law also works on these quantities. So We can write Ohm’s Law as V= I × Z Where,  V= Voltage, I= Current, Z= Impedance Resistor, Inductor and Capacitor are everywhere in e...

IN GENERAL :‑ The transformer oil basically functions as a liquid dielectric medium and as a coolant in transformer and in switchgears. This is a pure hydrocarbon mineral oil and is characteristic are generally in accordance with IS : 335. The electrical apparatus and equipment operate under conditions of high electrical stress and also are exposed to conditions of ageing within them. The transformer oil acts as an electrical divider between core and the tank and also as a medium to dissipate heat. The safety and safe operation of such equipment together with uninterrupted operation is of paramount importance. The presence of air and the effect of temperature gives rise to slugging and acidity and thereby deteriorates the transformer oil requiring periodic filtration / replenishment. CHARACTERISTIC OF TRANSFORMER OIL :‑ The purpose of use of transformer oil is dissipate heat by conduction through the solid insulation to the oil which by conservation effects eithe...

Overhauling of transformer is required either due to ageing of transformer or due to fault of transformer & after rectification of fault following steps should be followed for better overhauling. Draining of complete oil in tank or barrels before draining the oil, the oil in the transformer tank should be heated up by a separate hot oil circulation at around 70’C. So that when the oil is totally drained out, the core & winding assembly will have temperature higher than ambient. This will note be exposed without oil for more than 12 hrs. Before this period either the assembly should be filled with new oil or nitrogen or should be subjected to vacuum. Before draining the oil, the external surface of tank & fittings should be cleaned to locate the point of leakage Overhauling of OLTC which includes: Hot oil washing of diverter & selector chamber after untanking diverter switches. Untanking diverter switches Cleaning of fixed & moving contacts ...

Electrical equipment earthing  is for safety purpose. Equipment earthing can prevent workers from severe shock hazard. Live parts of Electrical equipment are always earthed in electrical system every where. There are so many advantages of equipment earthing:- (1) Equipment earthing can reduce electromagnetic interference (2) For Protection and Fault detection purpose Equipment earthing is important. Every Electrical power plant, Substation, Company has Equipment provided with proper Earthing. In Our home every appliances should be provided with earthing for safety point of view.

Polarization Index  is ratio of Insulation Resistance after 10 minutes (When Insulation Resistance value becomes stable) and Insulation Resistance Value Measured after 1 Minute. Polarization Index Indicates Dryness of Insulation of Any electrical equipment. So. Polarization Index= (10 Min. I.R. Value)/(1 Min. I.R. Value). Polarization Index must be more than 1.25. If, P.I. is less than 1.25 than it shows poor Condition of Insulation. One, another way to check insulation Condition is Tan-Delta test.

What is Reactive Power  is the question, that every one can not give clear answer. Reactive Power is nothing but Power required to charging Capacitors and building magnetic field in inductors. Pure Capacitors and Inductor does not consume Active Power. Pure Capacitor in shunt generates Reactive power and Pure Inductors in Series consumes Reactive Power. So, Capacitors and Inductors are reactive components. Reactive Power = √3*(V ph to ph)*(I)*Sin Ø Some thing about Reactive Power is:- Reactive Power is in quadrature with active power. Reactive Power requirement of the transmission line, Transformers, Motors is fulfill by installing shunt capacitor at load end or at sub-stations. For extra high voltage lines, in low load condition reactive power control of line can be done by installing shunt reactors at the EHV sub-stations. Voltage of the system is very much affected by reactive power. The reactive power supplied to an A.C. circuit is the product of t...

Indian electricity act-2003 in detail is:- Three erstwhile Acts that regulated the electricity sector: The Indian Electricity Act, 1910 The Electricity (Supply) Act, 1948 The Electricity Regulatory Commissions Act, 1998 The Indian Electricity Act, 1910 Provided basic framework for electric supply industry in India. Growth of the sector through private licensees.  Licence  by State Govt. Provision for licence for supply of electricity in a specified area. Legal framework for laying down of wires and other works. Provisions laying down relationship between licensee and consumer. Main amendments to the existing Acts Amendment in 1975 to enable generation in Central sector Amendment to bring in commercial viability in the functioning of SEBs – Section 59 amended to make the earning of a minimum return of 3% on fixed assets a statutory requirement (w.e.f 1.4.1985) Amendment in 1991 to open generation to private sector and establishment of RLDCs Amendment in 19...

i)          CONDUCTORS:       Usually 3 for single circuit line but 6 for double circuit line. Usual material is Steel reinforced Aluminum having high Electrical Conductivity and High Tensile Strength. ii)         STEP UP & STEP DOWN TRANSFORMERS: iii)        LINE INSULATORS:           To isolate conductors electrically from the ground. These should have High mechanical strength, High Electrical resistance to have min leakage current to ground, High relative permittivity in order that die electric strength is high, Non porous and with high ratio of puncture strength to flashover. They are PIN TYPE, SUSPENSION TYPE, STRAIN INSULATOR, SHACKLE INSULATOR iv)        SUPPORTS:   These are generally steel galvanized towers  to support conductors. v)...

Standard Practices: 1.           Permanent wiring 2.           Every lead should end at a terminal block. 3.           No junction by twisting. 4.           Copper stranded leads for CT/PT. 5.           ‘O’ lugs for CT, not ‘U’. 6.           Nut with washer is compulsory for CT termination. 7.           TBs shall be stud type and not screw type. 8.           Wherever two DC sources are available, Primary and Back-up protection DC should be from different sources. 9.         ...

The relay should be tested a.     Annually b.     Whenever mal-operation is suspected c.      While revising the relay settings 2.           Breaker opening and closing time a.     At the time of commissioning b.     Annually during service c.      Whenever trip or closing coils are changed d.     Whenever major repairs to opening mechanism are done e.      Whenever breaker contacts are changed 3.           Station Earth resistance →   Annually 4.           Meggering (IR value) of Transformer, CT, PT & CB a.     At the time of commissioning b.  ...

Leakage indication lamps should be compulsorily connected. ·        Every DC takes off should be through fuses (H.R.C.) or MCB. ·        Leakage in DC should be attended on top priority. ·        Check electrolyte level in cell every morning. If low, top up with distilled water. ·        Check up the voltage & specific gravity of six cells in each shift and record. ·        Ensure battery in floating condition normally. ·        Never charge at a voltage higher than 2.4 V/Cell. ·        If any cell found with low volt/sp. Gravity, bypass & charge separately and then replace. ·        Once in a day AC to charger should...

The major factors which causes the Accidents are as follows. Negligence of duty. Improper Planning of work. Improper working method. Lack of knowledge. Over enthusiasm. Avoiding procedures laid-down and avoiding safety measures. Hastiness. Improper communication. How to avoid Accidents in Electrical System? The personal working should take Line Clear Permit (LCP) and should ensure that the portion in which the work is to be done is electrically isolated & earthed. Operator should put indication plate invariably clearly indicating that      “ Man at Work “. The In charge of work should ensure that the portion in which work is to be carried out is properly earthed & cordon the work site with boundary in which the man has to work. The In charge should clearly explain the entire scope of work & the role of each person. The In charge should ensure that the person working is equipped with ...

Here is the  Scientists, mathematicians and physicists  who have given their Valuable and remarkable contribution for electrical engineering which we have as on today. 1.)    William Gilbert (1544 to 1603):- He was English Physician and founder of Magnetism. He is famous for his book “De Magnete.” 2.)    Charles A. Coulomb (1734 to 1806):- He is well known for “Coulomb’s Law” and unit of charge is “Coulomb” named after him was the French physicist. 3.)    James Watt (1736 to 1819):- He was English mechanical engineer and inventor of steam engine. Unit of Power is “Watt” named on him. 4.)    Alessandro Volta (1745 to 1827):- He is well known for invention of “Battery”. Voltage is name given to electrical quantity because of Alessandro Volta the Italian physicist. 5.)    Hans Christian Oersted (1777 to 1851):- He has discovered that electric field is created by electric currents. He was Danish physic...

DC batteries are the heart of any electrical power station or electrical substation. Because most of protection, annunciation, indication and communication system of electrical power station or substation are work by DC power. In case of AC power failure the only best option for power source is DC battery set. That’s why DC battery has so much importance in electrical power system. Now, here is the method how you can replace Faulty DC battery cell without interrupting DC power supply at  Electrical Power station or Electrical Substation. If we want to Replace DC Battery cell “B” from Whole Battery set. Take one crocodile short Link and connect its Red marked clamp with positive terminal of DC Battery cell “C” and Black marked clamp with Negative terminal of DC battery cell “A”. Diode in short link will be reverence Bias for Battery Cell “B”.  Also it will provide path to flow Electron current from Battery cell ...

Touch voltage  (or  Touch potential ) and  Step voltage  (or  Step potential ) are the significant term of electrical power system and mainly in electrical substations. Touch potential (Touch voltage):- As shown in above figure, suppose there is a structure which is faulted and fault current flowing towards ground through that structure. If a person standing on ground raises finger and touches that faulted structure than potential or voltage difference between that person’s finger and feet known as Touch potential or touch Voltage. Step potential (Step voltage):- At the time of fault suppose one person is moving on substation ground, at that time potential (voltage) between two steps of that person is known as Step potential (Step voltage). This Touch potential (Touch voltage) and Step potential (Step voltage) should be below 45V. so that a person working in electrical substation does not get shock.

India has five regional grids according to geographical area which covers the different state’s electrical power system. Each regional Grid has its own control center known as Regional Load dispatch center also known as Regional Load control center (RLCC). Over these Regional grids, there is National Grid have control center in Delhi Known as National Load Dispatch center also known as National Load Control Center (NLCC). National grid of India is nothing but Interconnection between regional Grids by interconnected AC lines and HVDC lines in electrical Power System. So, Under National Grid with National Load control Center (NLCC) Delhi has five regional grids:- 1)      Northern regional grid 2)      Western regional grid 3)      Southern regional grid 4)      Eastern regional grid 5)      North-East regional grid These five Regional grids cover all...

Here are some remarkable years or land mark in electrical power sector of India. In 1887 First hydro based power plant was commissioned at Darjeeling in electrical power system of India. In 1890 first steam based power plant was commissioned at Calcutta in electrical power system of India. In 1955 first 132Kv AC transmission line was commissioned in electrical power system of India. In 1959 first Nuclear power plant at trombay in electrical power system of India. In 1961 first 220Kv AC transmission line was commissioned in electrical power system of India. In 1964 different load dispatch center formed in electrical power system of India. In 1975 first 400Kv Ac transmission line between Dehar and panipat was commissioned in electrical power system of India. In 1978 first 500MW, 220Kv Thermal Power station was commissioned at Trombay and first 500 MW, 400Kv nuclear power station was commissioned at Tarapor in electrical power system of India. In 1978 SF6 and Vacuums circuit brea...

Suppose a single circuit AC transmission line. In Single circuit AC transmission line 3 conductors of all the 3 phases are unsymmetrical placed. Due to unsymmetrical spacing of the conductors Inductance and Capacitance of each conductors becomes different. Suppose we assume that resistance is same for all the three conductors than due to difference in inductance and capacitance, all the three conductors will have difference in Impedance. So, due to difference in impedance Voltage drop is different and unbalance of voltage is obtained. This is the reason why Transposition of Conductors requires in Electrical Transmission line. Transposition of electrical transmission line is must when Long AC transmission line is to be erected. Because Voltage unbalance in Long transmission line becomes remarkable and cannot be tolerated. In case of short transmission line it does not require and not create much imbalance in voltage. So, to make this voltage unbalance to minimum, the conductors are ...

Float charging  is used where load is constantly connected with DC batteries.  In Float charging Load, DC Batteries and Float charger are connected in parallel. Batteries are constantly connected with load. So, float charger provides load current and charging current to battery. In, Float charging the rate of charging is equals to battery self discharging rate. Battery chargers are providing with Float and Boost charging mode and also each mode with Auto and Manual Mode. Float voltage to be set in charger depends on type of battery, temperature conditions, etc. In every Battery charger two sections are there (1) Boost charger (2) Float charger.

Trickle charging  can be used for charged battery not for empty battery. Battery has its internal resistance through which its discharges very slowly known as self-discharging of battery. To overcome that effect  Trickle charging should be given to put battery in fully charged condition. Trickle charging Battery is not permanently connected with charger in trickle charging, but by one day, by a week or by a month trickle charging should be given to battery to get its fully charged condition.

Neutral earthing in Electrical System  is the Very important for Equipment like Transformers, Generators, etc. Earth (Ground) has very low resistance. Earth (Ground) big conducting medium. Neutral Earthing is always connected with 3-phase star point of the Transformer. Generator’s star point is also connected with Neutral Earthing. In Bipolar HVDC substation Neutral Point is also Earthed/Grounded. Neutral Earthing has so many Advantages. Because of Neutral grounding earth fault protection becomes easier. Neutral Earthing draws unbalanced current in case of system gets unbalanced. By measuring that neutral current protection can be applied. Neutral grounding provides a very stable neutral point to whole system. As the Neutral is grounded, Phase to Earth voltage will not rise. Neutral Earthing can also reduce insulation failure. So, Neutral earthing really helpful for system.

Skin Effect and Proximity effect are related to electrical terms Current and Current Density. In Conductors Skin Effect and Proximity Effects are present due Electromagnetism produced by Alternating Current flowing from it. Skin Effect and Proximity Effect are the important term in power system. They are considered at the time of designing of Conductor of Power Transmission Line. Skin Effect Suppose there Conductors from which Alternating Current is flowing. Now what happens is due internal flux linkages Current density near the outer surface area is higher and it is gradually decreases toward the axis of the conductor. This Non-uniform current density causes higher current flows near the surface of the conductor than the core for Alternating current. This Effect is Called “Skin Effect”. Skin Effect becomes higher as the Frequency increases. Also due to skin effect DC resistance of the conductor becomes higher. Skin Effect is absent in Direct Current (DC). Proximity E...

The impedance of a transformer is expressed in terms of impedance voltage. It is defined as the voltage required to be applied to the line terminals of a winding to cause rated current to flow through these terminals, with the terminals of other winding being short circuited. It is also called short circuit voltage (Vsc) The value is related to reference temperature It is determined by conducting short circuit test & Expressed as % of rated voltage, % impedance in the range of 4.5% to 15% Significance of Impedance voltage Determines the regulation and efficiency of a transformer Its high value means higher impedance, higher voltage regulation, higher losses and lesser efficiency.

A bundle conductor is made up of two or more sub conductors per phase.  Bundle conductors are called duplex, triplex, quadraplex, etc. By utilizing bundled conductors, line inductance is reduced considerably with the incidental advantage of increased power transmission capacity of the line With the higher effective diameter of the bundle conductor , the corona inception increases Bundle conductors are used for EHV sub stations and EHV lines generally for 400KV & above voltage system A bundle of 4 moose conductor is used on 400 KV bus and a bundle of 2 moose conductors is used on 400KV lines.

The load at which the reactive power absorbed by inductance of the line is equal to the reactive power supplied by the capacitance of the line is known as Surge Impedance Loading (SIL) Surge Impedance of a Transmission line     Z s  =√L/C Where L= Inductance of the line per phase C=Capacitance of the line, phase to neutral If the line is loaded such that the load impedance is equal to the Surge Impedance (Z s   ) of the line, the power carried by the line is called Surge Impedance Loading (SIL) P n  = V I = V 2 / Z s Line loading is expressed as a multiple of SIL. eg. 1.2 P n SIL mainly depends on voltage class and the conductor configuration of the line. For the load equal to SIL, the voltage of the line does not change along the length of the line. Hence no extra compensation for reactive power is required. If the load carried by the line is less than SIL, it is said to be lightly loaded and if the load carried is more than SIL, it is...

At higher voltages, the localized high electric fields ionize the air surrounding the surface of the conductor giving a violet visible discharge, called corona. The physics of this process sees it as excitation of nitrogen molecule in the air which emits ultra violet radiation, generally in the wave length range of 200 to 405 mm It is an external phenomenon dependent only on voltage It is accompanied by hissing sound, vibrations, power loss and radio interference The phenomenon of corona is accompanied by predominant third harmonic current which cause radio interference in the adjacent communication circuits. Corona causes increase in effective conductor diameter and reduces surface stress Location of corona It is observed on hard ware, at the point of connection between the conductors, along the busbar, equipments, etc It is often observed on the first insulator in a string where the electric field tends to be the greatest Looped excess wire around the ...

Here We will discuss how poor power factor affects power system. Apparent power = √3 VI /1000 Real power= √3 VI Cos Ø /1000 Reactive power= √3 VI SineØ/1000 Hence KW= KVA x Cos Ø Here, V= Voltage, I= Current, Ø= Angel between voltage and current vector, CosØ= Power factor (a) The amount of KW which can be supplied to load from the same KVA rating of power Transformer depends on power factor With higher power factor, higher KW can be supplied from the same power transformer (b) With given KW load of a motor or other load, poor power factor means higher KVA. Hence, Higher current for the same voltage. This gives rise to more I 2 R t  losses, hence loss of electrical energy (c) Higher current ‘I’ gives higher IZ drop in supply circuit. Hence, higher voltage regulation problems. Thus poor power factor gives poor voltage control, higher losses and poor use of electrical equipment rating. So, Power factor correct...

At the time of Electrical Installation various Testing equipments used by Electricians according to their need. It can be single function or multifunction equipments. New Electrical Installation should be tested before its commissioning and charging. Testing equipments should meet certain international accepted standards. Here we will understand the operation of Various Electrical testing equipments:  1) Themography Equipment Electrical equipments generates heat under operating conditions. At the time of Overload and loose connections heat generation is more. As show in above picture, Different colors shows difference in temperature. So, Ultimately, we will come to know the heating produce by the equipments or at the connections of different parts.  2) Phase Sequence tester Phase sequence tester is used to check correct phase rotation of 3-phase supplies. Rotating Lamps or indicators shows phase rotation of 3-ph system at particular measuring point. 3) Low Resistance...

Width of maximum right of way permitted as per forest conservation act ‘1980 and its subsequent amendment dated 25 th October, 1992, are as per Table 1.  Researches are being carried out for further optimizing the Right of Way. Guidelines of forest environmental rules shall be followed to avoid excessive tree cutting i.e. all the trees should be cut from root level in the 3 m corridor below each line conductor / earth wires.  In the balance corridor, trees branches are only to be lopped to attain the specified clearance as per Table 1. Table 1  – Guidelines for Right of Way as per forest conservations act 1980 and subsequent amendment dated 25 th October, 1992 Line voltage (kV) 66 110 132 220 400 500 HVDC 765 Row width (Meter) 18 22 27 35 52 52 85 Electrical clearance:   Electrical clearance while power lines crossing each other. In case of power line crossings, minimum clearance between lowest conductor of line and ground wire / top conductor of ...

As per section 33 of Electricity Act – 2003 (Central Act 36 of 2003), SLDC-State Load Dispatch centers performs:- SLDC- State Load Dispatch Center suppose to carry out following functions or Roles and Responsibilities of State Load Dispatch Center. Scheduling: All Open Access users (excluding wind and mini hydel and generating stations having total capacity not less than 5 MW and up to 15 MW opting for injection under UI) that are connected to the Grid shall schedule and dispatch according to instructions given by SLDC. The methodology of scheduling shall be according to provisions of Gujarat State Grid Code and Clauses 26 and 44 of GERC Tariff Regulations. Gaming: SLDC should see that no gaming is done while declaring capacity by generators. Energy Accounting: A State Energy Account, for the billing and settlement of ‘Capacity Charge’, ‘Energy Charge’, ‘UI Charge’ and ‘Reactive Charge’ shall be prepared by the SLDC. The SLDC...

Following Procedure should be done:- 1) Requisition form for 400Kv Line Clear Permit duly signed by maintenance engineer should be obtained. 2) Ensure that outage of the proposed line is confirmed. 3) Inform opposite end of the 400Kv transmission line and all other concern  before switching OFF breaker. 4) First switch off load end breaker & than Source end breaker of 400Kv Transmission line. 5) Check the Lamp Indication, semaphore for opening of breaker. 6) Check Current transformer relay switching and Potential transformer switching Relay. 7) In Substation Yard just check that all the three poles are opened. 8) Always use Hand gloves for opening and closing Isolator/Earth switch. 9) Open bus & line Isolator from both ends. 10) After confirming opening of isolators at both ends, provide Earthing at both the ends. 11) While providing Local Earthing, Connect Earth wire to the Earthing strip first & then Connect earthing Rod to the Equipment. 12) Ones Bus ...

The Electron, Name of Electricity came from the Greek word elektron. But tragedy is we haven’t seen electron yet. But we can measure it by various measurement devices like meters, oscilloscope, etc. We have also found ways to make them turn motors, light up light bulbs, and power cell phones, computers,and thousands of other really cool things. What is electricity though? Actually, that is a very good question. First we have to understand fundamental of  Atom . Atom is made up of three types of particles. they are proton, neutron and electrons. Proton has positive charge and electron carries negative charge. proton and neutron are larger in size compared to electron. Proton and neutron are not same in size but they have equal and opposite charges. So that net charge becomes Zero. Electrons are moving in orbits. When we apply energy, electron becomes free and atom has net positive charge and also called iron. Now amount of energy require to make electrons free depends on...

A Distribution Transformer is Energized All day on Primary side with Varying Loads on Secondary Side. Consumer’s Power Consumption varies with time to time during whole day, So Loading on Distribution Transformer is not uniform. Copper loss depends on Loading of Transformer, So during All day as Load changes copper will also change. All day efficiency is mostly less than commercial efficiency of Transformer. For Calculating All day efficiency of Transformer we should know Load cycle of Transformer during whole day. Steps to calculate All day Efficiency:- Calculate Output Energy of Transformer. Calculate the Loss of Energy due to Iron Loss. Calculate the Copper loss at various time intervals. Do sum of above three as input, from this calculation find All day Efficiency.

Electrical Power Transmission Line is nothing but “Connection” between Electrical Power Generating Station And Electrical Power Distribution Station. Different Types of Voltage levels :- Low Voltage:- 230Volts 1-Ph, 440Volts 3-Ph High Voltage:- 11Kv , 33Kv Extra High Voltage:- 66Kv, 132Kv, 220Kv and 400Kv Ultra High Voltage:- 765Kv and Above Electrical Power Transmission parameters:- An Electrical Power Transmission Line can be explained by series combination of Resistance(R), Conductance(G), Inductance(L) and Capacitance(C). These all Parameters are uniformly distributed along the whole Transmission Line. These parameters are related to Line Geometry, Operating Frequency and Construction. 1. Resistance (R):- Effective Resistance of Conductor, R = Power Loss in Conductor/I^2 For DC Resistance, R=ρl/A where, ρ= Resistivity of Conductor l= Length of  Conductor A= Area of Cross section of Conductor Value of Resistance(R) is generally Low in Electrical power transmissi...

Different protections applied for capacitor bank are as below:- External fuses (for 11KV) and Internal fuses (for 22/66/132 KV capacitor banks) of adequate thermal capacity to take care of internal faults. IDMT over current & earth fault relay for over current and earth fault protection. Over voltage, instantaneous no voltage protection & power factor control. Neutral Current Transformer (NCT) for current unbalance detection in case of 22/66/132 KV double star capacitor banks. Residual Voltage Transformer (RVT) for unbalance voltage detection of 11KV single star bank as well as for quick discharge. Series reactors to limit parallel switching current and to reduce the effect of harmonics. Off load isolators/ load break switches to isolate capacitor banks. Capacitor switches for switching pole mounted capacitor banks. Discharge resistors to reduce residual voltage from crest value of rated voltage to 50 volts or less within 5 minutes.

In EHV system, majority of faults occurring in over head lines are of transient in nature. 70 to 80 % of faults are of transient nature i.e. fault is removed after some time. In case of transient fault, if the line is disconnected from both the ends for a very short period, say about 1 sec, to allow fault arc to deionized and regain its dielectric strength, the line can be recharged at both the ends immediately afterwards. The security of the supply system is thus enhanced considerably and the stability of system is also maintained. Presently, auto reclose feature is applied with all 400 KV lines of Electricity company and 400KV inter state lines. Selection for auto reclose can be 1 phase or 3 phase. If auto reclosing produces very much less torsional fatigue than 3 phase auto reclose. The main advantage of If auto reclose is that during the De-ionization time, when one phase is opened, power transfer takes place through the other healthy phases & neutral and thus synchroniza...

Relay operates for 1 phase, 2 phase and 3 phase fuse failure in the supervised circuits and for an interruption in any of the cables or their associated fuses. When a fuse blows, the relay operates fast enough to inhibit the undesired operation of high speed distance relays. Uses the principle of instantaneous amplitude comparison of two voltages used for Fuse failure relay. This is achieved with two voltages , one before the fuse and the other after the fuse. Under normal operating conditions, the two voltages give rise to zero resultant voltage, thus no operation of Fuse failure relay. When the fuse blows out, the neutralizing effect is lost, hence Fuse failure relay operates.