Distribution Feeder Voltage Regulation and Control W. H. Kersting Milsoft Utility Solutions

Purpose of This Paper Present ANSI Voltage Standards Present Step Voltage Regulator What it is Control Settings Model IEEE 13 Node Test Feeder Steps in regulating voltage on the test feeder

The ANSI Voltage Standards Range A Nominal Utilization Voltage = 115 volts Maximum Utilization Voltage = 126 volts Minimum Service Voltage = 114 volts Minimum Utilization Voltage = 110 volts Range B Maximum Utilization Voltage = 127 volts Minimum Service Voltage = 110 volts Minimum Utilization Voltage = 107 volts

ANSI Range A Critical Voltages

Voltage Drop Assumptions 1 Volt drop on the service drop 2 Volt drop on the secondary 3 Volt drop through the transformer Minimum Voltage at the Transformer Primary Terminals will be 120 volts

Voltage Profiles

Step Voltage Regulator

Type B Step Voltage Regulator

The Step-Voltage Regulator Model

Three Phase Voltage Regulator Model

Model Matrix

Compensator Circuit

Control Panel

Control Circuit

Regulator Control Settings Voltage Level – voltage to hold at the regulation point R and X setting (volts) – Equivalent impedance from the regulator to the regulation point Time Delay – time after a tap change required before the tap is changed Bandwidth – allowed deviation from the set voltage level

Compensator Impedance

Equivalent Line Impedance

Bandwidth

IEEE 13 Node Test Feeder (Modified)

Modifications Line 4-12 changed to phases B-C Transformer 6-7 changed to Ungrounded Wye – Delta Load at Node 7 converted to Delta-PQ Load at Node 8 converted to Delta-PQ Load at Node 14 changed to phase B with constant Z load Load added at Node 5: 300 + j145.3 kVA

Step 1 Select regulation point to be Node 4 Run power-flow with source set to 126 volts Display Voltage Profile Compute compensator impedance

Step 1 Voltage Profile

Voltages and Currents from Power-Flow Run

Compensator R and X Settting

Full Load with Regs, no Caps

Observations Regulator taps Concern about high voltage at Node 2 Phase a: 11 Phase b: 12 Phase c: 15 Concern about high voltage at Node 2 Need to add shunt capacitors

Shunt Capacitors Source reactive power Install shunt capacitors Phase A: 765 kvar Phase B: 809 kvar Phase C; 1105 kvar Install shunt capacitors Node 3: 100 kvar per phases a,b,c Node 4: 600 kvar per phases a,b,c Node 13: 150 kvar on phase c

Full Load with Regs and Caps

Observations Regulator taps Notice good voltage balance Phase a: 5 Phase b: 6 Phase c: 7 Notice good voltage balance All voltages between 120 and 122 volts at Node 4

50% Load with all Capacitors

50% Load with 900 kvar at Node 4 switched off

10% Load Growth with original caps

10% Load Growth 100 kvar per phase added at node 4

Questions?