Relays

The workhorse of the electromagnetic protective relays is the induction disk type, which is used to provide a time delay function after pickup with a delay that corresponds to one of several inverse time characteristics that differ by the amount of steepness in the curve. The induction disk relay requires calibration to obtain accurate pickup and time characteristics that follow closely to that shown on the manufacturer's time current curve. Various things can happen over time to cause the re ...

There are different types of relays and each type has specific applications. It looks that you are looking for overcurrent setting calculations, as can be seen from mentioning plug setting and time setting multipliers. This is a typical protection scheme in distribution systems, the story is different at transmission levels.

There are many commercial software packages available that can be used to do the calculations, but again you need to build fundamental knowledge in order to in ...

The Buchholz relays I am used to dealing with have two levels, a Gas Alarm (Volume) and Gas Trip (Surge). They have a nitrogen injection port on the tank side of the Buchholz to inject to test each of these contacts, and a bleed port from the top of the Buchholz which allows for the nitrogen or fault-gasses to be captured for laboratory analysis.

Obviously an open flame is a low-tech way of determining if there are short-chain hydrocarbons present in the gas in the Buchholz, but if ...

All electrical equipment has a definite life span and its replacement depend upon the manufacturer's advice. However I would advise periodic inspection to see the condition of the relay or contactor such as condition of the coil if its visible from outside, including any testings if required; the condition of the contacts, to see they are clean, carbon and rust free, and in good contact or in open position as the case may be; and the connection of the wires to the terminals and the terminal t ...

They can be very "black box"-ish, design in easily and work for decades without a squeak. Or, they can be a nightmare of unanswered questions and inexplicable failures.

It is vitally important to ensure that relays are selected which are appropriate for the current, voltage, atmosphere/environment and use, as many have mentioned. Sometimes, research pays off handsomely if it starts before specification.

For instance, contact shape and composition can have unforseen effec ...

A relay operates like an electromagnet. A relay is a switch; which can make contact between two points. Here, there are three such points; COM (common), NO (normally open) and NC (normally closed). The COM will be connected to NC in normal state. The input to the relay, excites an electromagnet (relay coil) so that the normal connection (i. e. , between 'com' and 'NC' terminals) gets switched, so now the connection is between com and NO.

The relay is just a switch. It just do the ...