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

2. 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..

3. Types of Operational Modes
Open Transition
Closed Transition

4. 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.

5. 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

6. 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.

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

8. 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.

9. 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

10. 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

11. 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

12. 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