TIMING APPLICATIONS OF GPS High Energy Transmission with High Precision GPS Time Gaurav Sharma John Hannah Vivekanand Sivaraman

ABOUT BPA oBonneville Power Administration – Power Supplier in the Pacific North West. Serves Oregon, Washington, W Montana, and most of Idaho. o o390 switching stations o16500 MW Power Capacity & 8600 MW annual delivery o181 Customers including industries and public utilities

Timing Applications in Energy Transmission Power generation and Power transfer Power Outages Disturbance Records Fault Location Real Time Phase Measurements

BPA: Timing Techniques and Problems Central Time System –Not enough accuracy for Fault locators –signal subject to distortions High frequency pulse over Microwave for Fault Locators –Used up a lot of available bandwidth Local Time Code Generators for remote stations –Time code generator needs to be manually resynchronized every couple of months – no resetting at regular interval Radio reception from GOES or WWV –GOES receivers off the correct time. –GOES signal subject to interference and eclipses. –GOES satellite system problems – repositioning - requires antenna repointing. GOES: Geostationary Orbit Earth Satellite WWV: Radio Station, Fort Collins, Colorado

BPA: Timing Techniques Problems Possible Solution: GPS 1 microsecond accuracy Multiple satellite redundancy High Reliability BPA Lab Testing – showed high accuracy, precision and reliability in timing.

GPS Implementation in Central Time System New system - 3 primary sources, 1 voting switchover unit + Monitoring Systems Primary sources equipped with GPS receivers, each having an antenna and a power unit. 2 with battery back up. 1 has a rubidium oscillator in the event of GPS input failure. Improved Switching Tolerance (1 Microsecond level) (What is switching?)

GPS Implementation in Fault Location and Rectification When a fault occurs on a transmission line a high frequency wave propagates in both directions from the fault. Compare the arrival time at switching stations on the either side of fault for locating it. Problems with Old System: –Synchronization pulse used a lot of bandwidth (expensive) over the analog microwave system –Available to major stations only GPS Implementation: –Initially, for the synchronizing the pulse to UTC only - –Later, also as FLAR units –Available to even minor and remote stations

GPS Implementation in Phasor Measurements Phasor: a vector representation of a sinusoidal quantity that includes a magnitude and a phase angle. The power system in North America is a three-phase 60Hz sinusoid. Phase angle between two stations determines the power transfer between stations. Phasor observations used for monitoring. (Require 0.1 electrical degree accuracy for monitoring Or 5 micro-sec synchronization between monitoring units.) GPS used as precise timing source.(The accuracy of time measurement ~1 micro-sec).

Conclusions Expensive upgrades and redundancies were avoided. GPS provided a comprehensive way for implementation of accurate timing system – no need for different timing system for every other system. Stood the tests for accuracy, reliability, coverage and cost.