Closed Transition ATS’s John J. Stark Marketing Services Coordinator, Russelectric Inc.

Why Operate in Parallel with the Utility? Closed Transition Transfer of non-utility generator, re-transfer and generator test Cogeneration Peak Shaving Curtailable Rate Structure Distributed Generation I would expect most of you have a good idea why a facility would want to parallel with the utility. Since this discussion is based on parallel operation with the utility, lets take a second and quickly review the reasons one might parallel onsite generators with the utility Review Last item has gotten a lot of play these days particularly with deregulation and in many cases may be more attractive to the utility companies, than adding their own generating facilities..

Types of Operational Modes Open Transition Closed Transition

First let’s talk about open transition mode An open transition mode of operation is a method of transferring a load between two sources with an interruption of power during transfer.

L L L E E E N N N M1 M2 Open transition ATS Motor #1 drives the normal source contacts Open. M1 This is all done with very reliable mechanical interlocking and does not require an elaborate electrical interlocking design. The load source is disconnected for an adjustable period to allow regenerative power to decay Motor #2 then drives the emergency source contacts closed M2

Closed Transition Mode A closed transition mode of operation is a method of either: 1) Transferring a facility’s load between the utility and generator or 2) operating a generator in continuous parallel with the utility service, without an interruption of service.

Utility Concerns Reliability and quality of utility power to other customers Safety and protection of utility service personnel Protection of utility equipment

Type of Parallel Operation Passive Momentary utility parallel operation 100ms or less There are basically two types of parallel operation of a NUG (Non-Utility Generator) with the utility 100 ms overlap is accepted by many utilities with no interconnection requirements at all. However, some utilities have some minimum requirements while still others treat it no differently than if the NUG were operated in parallel for an indefinite period of time The minimum requirements for short time operation in parallel could be a simple timing circuit that times out if the contacts are in parallel for a definite set period of time and send a signal to trip the utility breaker if this time is exceeded. Still others might have some minimum protective relay requirements such aas the use of a device 32 or 27/59.

L E L E L E N N N S1 S2 Closed Transition Operation Closed transition ATS L N E L N E L N E Operator #1 drives the normal source contacts open S1 The load source is connected to both sources momentarily S2 Operator #2 drives the emergency source contacts closed Closed Transition Operation

Closed Transition Transfer Switches Advantages No interruption of power for load test and return to utility as well as peak shave operation Fast transfer operation

Closed Transition Transfer Switches Disadvantages No phase lock synchronizing No Protective relays No mechanical interlock, thus no safe manual operation Lacks true load test function Higher fault current requirements

Full 3-Phase over and under voltage and frequency Sophisticated Controls and Safety Features Full 3-Phase over and under voltage and frequency sensing on both normal and emergency sources. Protection against running over 100 msecs: Signals to operators Fail to Transfer Function Provides trip signals to the generator or utility breakers. Our Switches are controlled by the MODEL 2000 Microprocessor Control System. It Features: Full 3-Phase over and under voltage and frequency sensing on both normal and emergency sources. Voltage differential sensing for single-phase loss detection Over 30 standard accessories built in. RS 422/485 Communications Port. Windows based SCADA package available