PowerSouth Lowman AC/DC Essential Voltage System

Essential Voltage System• Original Design Weaknesses• Event Report• New Design

Original Design Overview

Original Design Weaknesses• Manual operation• Break-before-make switching• Lack of redundancy• Lack of Data/Alarms

480V Emergency Section• Manual breaker operation with Kirk-key interface

Diesel Generator• No adequate PM testing on Diesel Generator

Chargers/Batteries• Single point of failure with one charger

Inverters• Single point of failure with one inverter feeding

primary and secondary control power in some areas

Event Report

Event Recap• Normal operation• Unit 2 charger is impaired with no direct alarming

Event Recap (cont.)• Batteries become depleted• Switchgear relaying begins to alarm

Event Recap (cont.)• Standby Charger was swapped to Unit 2• DC breaker from Standby Charger tripped

numerous times

Event Recap (cont.)• AC Switchgear not able to transfer to station

service• No DC power • Turbine Trips and spins down without adequate

lube or seal oil supply.

Rotor/Bearing Damage

Hydrogen Seal Casing Damage

Need for Improvement• Safety• Reliability• Adequate feedback• Automated operation where possible

• Redundancy

Upgraded System Overview

480V Automatic Transfer

Normal Feed

Emergency Feed

480V Automatic Transfer Switch

480V Paralleling Switchgear

480V Paralleling SWGR

Diesel Generator/Paralleling

SwitchgearProtective Relay

Sync Indication

Unit 2 Feed

Unit 3 Feed

Diesel Gen Feed

350kW Diesel Generator

Redundant Charging with Standby

Utility Fed Charger

Emer. Fed Charger

Unit 2 Batteries

Standby

Battery Chargers

Unit 3 Chargers

Unit 2 ChargersStandby

Charger

Batteries

Unit 3 Batteries

Standby Batteries

Unit 2 Batteries

DC Switchboard/Distribution

DC Switchboard

Unit 2 Battery Breaker

2A Charger Feed2B Charger Feed

Dual Inverters

Inverter 2A

Inverter 2B

Dual Inverters

Inverter 2A

Inverter 2B

Inverter3A

Inverter3B

120V Essential Power Transformers

120V Essential Power Transformer 2A

120V Essential Power Transformer 2B

Control Screen

DC Voltage Visual

Critical Event Response

Open

Questions/Comments?