Thermal magnetic uses bimetallic strips- manual reset

fault sensing time is less in microprocessor release

trivector meter can measure  active power ,reactive 
power ,apparent power i.e.with the help of a single meter 
we can measure kva,kw,kvar.

Trivector meter is Electronic type Energy Meter which 
measures energy parameters, like active energy, Reactive 
energy,apparent energy, Power Factor, frequency etc. 
Through which we can know how much enregy recieved or 
sent.Trivector meter has 2 types, one is 3ph 3wire meter n 
other is 3 ph 4wire meter.
It is conneceted in the substation to incoming or outgoing 
feeders to know how energy is given out or recieved from 
other end, or to Transformers on HV n LV side to know the 
Transformer loss.

trivector meter is a device that measures the amount of 
electrical energy supplied to or produced by residence, 
business, or machine.
The most common type is more properly known as a  kilowatt 
hour meter or a meter. When used in electricity retaining, 
the utilities record the values measured by these meters to 
generate an invoice  for the electricity. They may also 
record other variables including the time when the 
electricity was used.
It is called as tri-vector meter because it measures the 
energy consumption of the three phase line

Tri-energies are Apparent, Active and Reactive. These are 
expressed in three vectors. A single meter that measures 
these three energy details are called a Tri-vector meter. 
This is clear from the name of the instrument itself.