Post on 14-Nov-2014
description
Power Transfer Switches- for -
IEEE-IAS - by -
James S. Nasby
Columbia Engineering
C.E. IEEE-IAS 2
Topics to be Covered
Arrangement I (Combo. Unit) Arrangement II (Separately Listed Units) Power Supply Considerations Options
C.E. IEEE-IAS 3
Note: “Alternate Source” may be a “Hot Emergency Bus” as often employed in hospitals.
In these systems, multiple MVA size gen-sets are used along w/ additional upstream Transfer Switches with a path to one or more Utility Connections.
This often results in very high fault currents on the Alternate Source Side.
Also note that two C/Bs will be required in all Arrangement I units per 2010 Edition of NFPA-20.
Two Arrangements
From the 2007 Edition of NFPA-20
C.E. IEEE-IAS 4
Revised to Three
NFPA-20-2013 Fig. A.10.8 1
Revised Arrangement I-A
perLogs #29 & #157
N E
Normal Source See 9.2
Arrangement I-A See 10.8.2.1
Alternate Source See 9.3
See 10.8.3
Note: Need to Renumber "Arrangement I" as "Arrangement I-A"
ATS
CB CB
IS IS
Was "Arrangement I"
See Log #103
Contactor
Listed Combination
Fire Pump Controller
and Transfer Power
Transfer Switch
Motor
C.E. IEEE-IAS 5
Arrangement 1-B
NFPA-20-2013 Fig. A.10.8 2Arrangement I-B
Proposed NewArrangement I-B
per Log #105
Upstream Transfer Switch
Normal Source See 9.2
Alternate Source See 9.3
To other generator
loads
See 9.6.5
Listed Combination Fire Pump Controller
and Power Transfer Switch
See 10.8.2.1 and 10.8.3
EN
N E
See NFPA 70
Article 230
Motor
Gen
"Hot" Emergency Bus
C.E. IEEE-IAS 6
Revised Arrangement II
NFPA-20-2013 Fig. A.10.8 3
Revised Arrangement II
perLogs #29 & #157
Listed Fire Pump Controller
Arrangement II See 10.8.2.2
EN
Normal Source See 9.2
Alternate Source See 9.3
CB
IS*IS*
CB**
ATS
Field Wiring
See 10.8.3 & 9.6.4
Listed Fire PumpPower Transfer
Switch Assembly (Service Entrance Equipment may
Be Separate)
See 10.8.2.2
Single or Separate Enclosure(s)
See 10.8.2.2(4)
See 9.6.5 & NFPA 70 §700.27
* May be Omitted
** May be located at generator if alternate source is a standby
generator.
Motor
C.E. IEEE-IAS 7
Power Supply Systems
Power Supply Weak = Voltage Drop Problems Stiff = Careful Coordination of WIC
Type of System Wye = Typical
Grounded Neutral = Typical Ungrounded = Care & Coordination
Delta = Great Care Needed. Ungrounded Corner Ground 4 Wire High Leg (240 / 120 / 208)
C.E. IEEE-IAS 8
Options (Variations)
Added Ground Lugs (Some Jurisdictions)
Fourth Pole (Neutral) Usually “Overlapping” (Make Before Break) Supplied by Some E.F.P.C. Mfrs.
In Phase Transfer Delays Transfer Until Motor Back EMF Phase Angle
is Close to that of the Intended Source Completely Useless for Pump Motors due to Very
Low Inertia and Large Minimum Load on Motor
C.E. IEEE-IAS 9
Arrangement I (Combo. Unit)
10.8.1 General10.8.2.1 Arrangement I
(Listed Combination Fire Pump Controller and Power Transfer Switch)
10.8.3 Power Transfer Switch Requirements
C.E. IEEE-IAS 10
Arrangement I – Combo. Unit
C.E. IEEE-IAS 11
Short Circuit (WIC)
Coordination
Note: “---” means no Upstream Protection is Required.
E.g.: Self Protecting (Blow Apart) Isolating Switch Provides Suitable Protection of the Internal Transfer Switch.
C.E. IEEE-IAS 12
Arrangement II (Separate Units)
10.8.1 General 10.8.2.2 Arrangement II
(Individually Listed Fire Pump Controller and Power Transfer Switch)
10.8.3 Power Transfer Switch Requirements
C.E. IEEE-IAS 13
Russelectric F.P. Transfer Switch
C.E. IEEE-IAS 14
Arrangement II Requirements:Who Supplies What?
10.8.2.2(2) "An isolating switch, or service disconnect where required, ahead of the normal input terminals of the transfer switch." Ever not required?
10.8.2.2(3) [and 9.2.3.4]: Xfer Switch OCP "shall be selected or set to carry indefinitely the sum of the locked rotor current of the fire pump motor" plus any additional connected loads. E.g.: 600% of motor FLA minimum
10.8.3.4.2: Transfer switch Minimum Sized at only 115% of the motor FLA current - Rarely Enough.
10.8.3.6.4: Phase Reversal Sensing
C.E. IEEE-IAS 15
Arrangement II Requirements:Who Supplies What?
10.8.2.2(4) An isolating switch ahead of the alternate source input terminals of the transfer switch shall meet the following requirements:
(a) The isolating switch shall be lockable in the on position. (b) A placard shall be externally installed on the isolating switch stating
“Fire Pump Isolating Switch,” with letters at least 1 in. (25 mm) in height. (c) A placard shall be placed adjacent to the fire pump controller
stating the location of the isolating switch and the location of the key (if the isolating switch is locked).
(d) The isolating switch shall be supervised to indicate when it is not closed, by one of the following methods:
i. Central station, proprietary, or remote station signal service ii. Local signaling service that will cause the sounding of an
audible signal at a constantly attended point iii. Locking the isolating switch closed
iv. Sealing of isolating switches and approved weekly recorded inspections where isolating switches are located within fenced enclosures or in buildings under the control of the owner
(e) This supervision shall operate an audible and visible signal on the transfer switch and permit monitoring at a remote point where required.
C.E. IEEE-IAS 16
WIC Coordination ExampleTransfer Switch Sizing Example for 100 Hp at 460 Vac
X 115% Thermal X 600% Breaker WIC Coord.
Motor Hp Motor FLAThermal Sizing Upstream Size Switch Size
100 Hp 124 amps 143 amps 150 amp 744 amp 800 amp 400 amp
In this Example, a 150 Amp Xfer Switch meets the 115% criteria; but, it’s Short Circuit (WIC) Rating will be invalid if the upstream device is larger than 250 amps. However, a 250 Amp OCP doesn’t meet the 600% criteria. Hence, a larger Xfer switch is needed. Who does the coordination, and who supplies what?
C.E. IEEE-IAS 17
Are All of These Supplied? 1) The two Position Indicator lights 2) The Engine Start delay timer and the Re-Transfer delay timer, 3) The Engine Start contacts, 4) The Test (Transfer) switch (pushbutton), maybe. 5) The Normal Side Service Disconnect and overcurrent protection fuses or breaker, 6) Otherwise, the required emergency side Isolating Switch which is: 7) Lockable "ON" 8) Having an external "Fire Pump Isolating Switch" placard, 9) A placard next to the controller giving the location of this Isolating Switch10) Supervision of the Isolating Switch by one of the four means given11) Audible and visible alarm to indicate Isolating Switch Open,12) Isolating Switch contacts for remote alarm,13) Means to prevent Higher-than-Normal motor in-rush currents,14) Phase reversal sensing and transfer circuitry.15) Although not required, the Bypass switch may or may not be standard equipment.
C.E. IEEE-IAS 18
Arrangement II Detailed Requirements
Application Guide- for -
Fire Pump Power Transfer Switches- for use with -
Electric Motor Driven Fire Pumps
By: James S. Nasby, Columbia Engineering,
This document attempts to outline the salient requirements for the selection coordination and application of fire pump transfer switches upstream of fire pump controllers in order to meet the requirements of NFPA 20 Standard for the Installation of Stationary Pumps for Fire Protection. Power Transfer Switches "Arrangement I" - Combined Transfer Switch & Fire Pump ControllerListed Combination Fire Pump Controller and Power Transfer Switch" units eliminate the majority of the required coordination since it is accomplished by the manufacturers of these combination units. Moreover, this coordination is examined, verified, and documented by both Underwriters Laboratories, Inc. and by Factory Mutual Laboratories. This is the simplest and most verifiable way to meet NFPA 20. Power Transfer Switches "Arrangement II" ‑ Separate Transfer Switch & Fire Pump ControllerThis arrangement consists of a listed Single Power Source (non‑transfer switch) Fire Pump Controller and a listed "Fire Pump Power Transfer Switch". NFPA 20 section 10.1.2.1 makes it clear that a transfer switch used for supplying power to a fire pump must be listed for the service. To wit: “All controllers and transfer switches shall be specifically listed for electric motor‑driven . . .
Note: A full copy is included with the handouts.
C.E. IEEE-IAS 19
Questions ?