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As per IEC 62271.1, the rated short circuit current has a time constant of 45ms (approximately X/R=14.1 at 50 Hz). If your application requires a higher time constants, you may purchase a breaker designed to operate on short circuit currents with a time constant of 120ms. Thus if you assume that the relay takes 10mS to detect the fault and actuate circuit breaker shunt trip, it will be interrupting more DC current if the time constant is 120mS, while the AC component remains same.

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Power Transmission lines are usually very long, EHV Transmission lines used for wheeling of power. They are strung on very high lattice Towers. The transmission lines are of ACSR or AAAC conductors of appropriate current carrying capacities. In case of wheeling of large currents at say 400kV level, bundle conductors are used. They don't need any kind of insulation or jackets etc. as the ambient air serves as Air insulation. Thus maintaining requisite flash over distance vis'a vis, EHV voltage ...

Why do we need to Split the Stator of Single Phase A-synchronous (Induction Motor) unlike the 3 Phase Induction Motor?

A 3 phase induction motor has 3 different currents flowing through it... these 3 cause 3 different magnetic fields that are oscillating at 120 degrees (ideally) apart, the interaction of these 3 magnetic fields in the air gap causes a rotating magnetic field, this magnetic field rotates at a speed we call synchronous speed, which is also the maximum speed the motor ca ...

Since there are several electrical standards: by frequency 50/60Hz, by low voltage (residential / commercial) use: 120-220-240-277-380-480V. and we could unify between European/American/Asian use changing all to DC 12Volts, which is used by cars. DC Green technologies are now present in power sources (solar panels) and most loads could be served in DC (led illumination, TVs and all electronic appliances) using USB co ...

Q: I know what is forward synchronization and reverse synchronization. But in the article I read its mentioned that reverse synchronization is dangerous.

1) Why is reverse synchronization dangerous?
2) What are the differences in parameters in auto synchronization for both types of synchronization?
3) If there is no auto sync relay, is there any difference when synchronized manually?

A: In the old days when you had mechanical governors with a lot of droop (the ...

When there is a phase to ground fault on the system and maintenance crew are trying to determine the source of the fault, they are even more danger considering first of all they are working on an energized system and the potential to having a phase to phase fault before resolving the first, can be potentially dangerous to life and the electrical system as a whole, also considering the heavy wear and tear of the insulation on the system and the shutdown time and cost if a fatally occurs. Why a ...

I wonder what is criteria for this test, which reasons important when design transformer for this test? Axial, radial forces or distance between low voltage and high voltage coils or other things?

The meaning of the short circuit proof design of a transformer is easy to understand: in case a short circuit happens in your grid and the damages are repaired, you don't really like to find after you switch on the power again that your transformer fails after short time.

IEEE C57.12 ...

What are some factors in choosing a Four Wire Delta System over a Four Wire Wye System or Visa Vera?

In the 4 wire delta or center tap delta there is usually limits of 5-7.5% of total kVA on the single phase loading. It was meant for control power for the 3 phase load only. I have found most do not get this and overload the center tap capacity. You can tell easily when you take off the cover and Center coil is cooked black and outside coils look good.
3-phase 4-wire wye: In the U ...

What are some other considerations that go into choosing a Three Wire Delta System rather than a Three Wire Wye System other than budget?

Basically, 3-wire 3-phase systems save one conductor, the neutral, in overhead construction.
In a service (600 volts and under) the source transformer winding is a delta or an open-delta. In California, if the voltage is 240V, then one of the corners is grounded. If it is 480V then it is ungrounded.

As a distribution system, the sou ...

Over sizing generators is guzzling energy (higher fuel), money (higher cost) and larger space (high footprint). By applying Harmonic Filter, that depending upon load types, say metal, rolling mills, or much easier loads like buildings, textile plants etc., one can load the Generator and Engine by nearly to 100% of its capacity sustainably. In the past few decades, we have done over several hundreds, if not thousands, of jobs applying Harmonic Filter with generators, both LT (415/ 433/ 440V) a ...

The people have described the single phase 120/240v system that is used in the USA, Canada, and Mexico, with the center-taped transformer. Japan uses a similar system but the voltage is lower: 100/200v. Most North America appliances work in Japan. Commercial and industrial systems in the USA run on three phase 208Y/120v or 480Y/277v. Canada uses higher voltage, typically 600/347v. These are all 60 Hz frequency.

Most of the rest of the world ...

Aircraft electrical components operate on many different voltages both AC and DC. However, most of the aircraft systems use 115 volts AC at 400 hertz or 28 volts DC. 26 volts AC is also used in some aircraft for lighting purposes, where the power is generated by a commutator which regulates the output voltage of 28 volts DC. AC power, normally at a phase voltage of 115V, is generated by an alternator, g ...

Someone told me the appliances for United States 240v, are combined with TWO 120v hot wires, a neutral, and a ground wire, like refrigerator? If yes, can it be power by one 240v hot wire (single phase), and neutral, ground wire?

There are very few appliances in the US that are 240v, most are 120V, with only the high current ones such as a dryer, stove/range, and some air conditioners. However it is unwise to assume that all 240v appliances only utilize 240v, many older units utiliz ...

Case: I am restoring a 1960s analog audio tape recorder for high quality audio use, the tape recorder is a USA model operating on 120VAC at 60Hz, the mains voltage in Singapore where the machine will be operated is 230VAC but 50Hz. Other converters that convert 230VAC/50Hz to 120VAC/60Hz have been unsuitable -- I hear high distortion and square wave noise to break through in to the audio in ...

Q: I have a situation where our UPS servicing data center rack systems are failing repetitively after replacements.

We know our mains transformer is undersized in terms of load capacity and under voltages are measured going to the input of the UPS that is providing back up power to data center in a rack mount. However these voltages measured were 110VAC and still within operating range. In another facility with the same rack systems, colleagues are saying they're seeing "brown out ...

A fault on an electrical system will continue until either a protective device operates to isolate the fault, the fault burns itself clear or the power source fails due to the load imposed by the fault, which can occur when the fault is supplied by local generators.

If the circuit has a properly adjusted protective relay and circuit breaker operating are: the relay processing time + breaker opening time + arc extinction. In the case of an unprotected circuit time will be the protec ...

Q: We have 02 motor generator sets each of same KW rating and speed etc running in parallel and having pure inductive load. Thrice it happened that 01 set got tripped on reverse power protection. 01 set operates with 0.65PF lagging while other runs with <0.5PF leading. After tripping of MG set, remaining set's current decreases from 42A to 35A. If we want to synch again two MG sets while plant is running at 100% power, is there any danger of tripping?(if remaining set got tripped, plant wi ...

As with all such questions, it depends (on the purpose of the studies, and the type of wind generator). What is modeled should be what is there. Induction generator turbines should use an induction motor model with negative real power (so that their fault current contribution, and reactive demand increase when (re) accelerating are captured). 100% inverted turbines are usually represented as a static P (possibly Q) load. Double fed turbines...may require careful thought. Obviously, dispatch/s ...

Basically there are just two type earth fault and restricted earth fault.
An earth fault is a leakage of current between any conductor that normally carries current, that is the phase and neutral conductors, and the general mass of earth and anything connected to it anywhere downstream of the point within the system that the earth fault protection device is situated. The protective device for this type of fault is often referred to as an unrestricted earth fault device.

A res ...

Question: I have a 1.5 kW three phase motor running on a GoHz VFD. The VFD is connected to two phase / 220V supply, the motor is connected in Delta connection. RPM of the motor is 2800 / 3360 at 50 / 60 Hz. It is now running on 50 Hz. I need a RPM of 1400 to 1500 which means I will need to run the motor on 25 Hz which is not a problem with the GoHz VFD. But how much does it affect the motor torque? ...