Calculating line impedance for distance relaying

Status
Not open for further replies.
B

Bugman1400

Senior Member
Location
Charlotte, NC
mbrooke said:
Which brings me to this: a 311C or 421 without differential or communication. For an LOV you can either trip the line, switch to over current protection only, or do nothing (no line protection). Correct? With line VTs only one set of relays have to make this hard choice, but with bus VTs either all of group A or group B (if not both) must decide.
Click to expand...

No, you can never have no protection. While we have been focusing on the technical aspect, its important to know the NERC regulation side of this.
Phase OCs are adequate for radial lines but, are nearly impossible to coordinate for network lines and are almost never used. The exception to this is initial line energization (for line VTs) and LOP conditions. So, you are correct that Phase OC is used during LOP.
 
mbrooke

mbrooke

Batteries Included
Location
United States
Occupation
Technician
Bugman1400 said:
No, you can never have no protection. While we have been focusing on the technical aspect, its important to know the NERC regulation side of this.
Phase OCs are adequate for radial lines but, are nearly impossible to coordinate for network lines and are almost never used. The exception to this is initial line energization (for line VTs) and LOP conditions. So, you are correct that Phase OC is used during LOP.
Click to expand...

Thats my point, over current is always a last resort, never even considered for networked lines as normal protection. As for line connected VTs, why do you need OC protection upon initial energization?



K8MHZ said:
Trial and error.
Click to expand...

Or fault scenarios that (fortunately) never occurred for said utility :angel:
 
Status
Not open for further replies.
Top