Wave trap,its name indicates that it is used to trap some waves.
Q.What is the use of wave trap in electrical system,where it used?
A.Wave trap is used for communication purpose in substations.
Q.We have the telephones in these days?then what is again these communication?
A.20 years back our country was not developed in telecommunication sector.then our electrical engineers developed a system that communication can be done through our power lines.it is called power line carrier communication (PLCC).
But in these days we are modifying with optical fiber inside the earth wire. it will take care of speech communication and protection.
Q.Can we transmit electrical power and communication at the same time with single conductor?
A.We can transmit,but with different frequencies.so they can be separated easily by wave trap at entrance of substation.
Generally electrical power waves has frequency of 50 Hz,so we send our communication waves with high frequencies like 150kHz,200kHz etc..,
Wave trap consists of filter circuit (combination of capacitor and inductor) which is used to allow only power frequency waves to electrical equipment's and stop the communication wave in to yard.
Q.Why wave trap is located at entrance of substation?what will happen if electrical equipment's receive communication waves?
A.As communication waves are high frequency (and not power frequency) they will act as harmonics towards electrical equipment's like transformer,breaker etc...,so in order to protect them we should connect at entrance (after the CVT) so that wave trap will trap the communication waves.
Q.What is the need of communication between substations?
A.If any fault in any substation,it should intimate to all connected substations to it.
each telephone is connected to only one particular substation only.