SOLUTION

Why is Mho’s Relay used for Long Transmission Line?

• Mho relay comes in the category of the distance relay protection scheme.
• The mho type relay is most suited for long lines because there are more chances of severe synchronizing power surges on the system.
• It does not need any additional equipment to prevent tripping during these surges.
• The mho relay occupies the least space on an R-X diagram for a given line section and is, therefore, least affected by abnormal system conditions except for the line faults.
• Since the mho relay is most affected by arc resistance, it is used for long lines.