UPS D9-11 1 Optical Design Options Nxt Phase

8/8/2019 UPS D9-11 1 Optical Design Options Nxt Phase

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IEEE PES Substation Committee Annual Meeting

May 1, 2000

Design Options Using Optical

Current and Voltage Transducers ina High Voltage Substation



Overview of Discussion

• History of NxtPhase origins.

• Basic description of current and voltage sensing

technology.

• Benefits of optical sensing compared to

conventional.

• Example case of using optical sensing

technology.



The new company has been formed by

combining the industry’s leading teams inoptical current & voltage sensing

Fiber Optic CurrentSensing Technology

Based on Gyros for

Military and AerospaceApplications

Integrated Optic

Pockels Cell for VoltageSensing Technology

A Powerhouse of Technology

30 People located in

Vancouver & Phoenix



FiberOptic

Loop

LightSource

CurrentCarrying

Conductor

PhotoDetector

CircularPolarizerModulator

Polarizer

Mirror

Fiber Optic Current Sensor



Electric Field Measurement w ith the

Integrated Optics Pockels Cell

Electric

Field

Linearly polarized light in.

y

x

Elliptically polarized lightout. (proportional to field)

y

x





Advantages of Optical Sensors

• No CT saturation or VT ferroresonance (magneticcircuit eliminated)

• No insulating oil or SF6required (NxtPhase unique)

• Zero footprint capability

• Voltage and current sensing in one device

• Low weight

• Wide, adjustable dynamic range (NxtPhase unique)

• High bandwidth, limited by electronics• Electrical isolation provided by fibers

• Metering and relaying in one device

• Leads to digital communication and data aquisition



IPP tap from utility breakers

IPP Metering Example

It is desired to revenue meter (ie 0.3% accuracy):

- outgoing generation

- station service load with no generation

IPP ownedequipment 138 kV

13.8 kV

Stn. Service Xfmr.

475 kW load

Utility owned equipment

Gas TurbineGenerators

225 MVA

13.8 kV, 60 Hz

Design Constraints at 138 kV:

Fault Level = 40 kA

Max. Gen. Current = 3000A

Stn. Service Load = 2A



Why Existing CTs Will Not Perform Adequately

Conventional CTs do not have revenue accuracy at the low

end of measuring range.

Solution?…Use two CT windings. One low range, one

high range.

No!

Wide dynamic range and high fault currents can cause

grief.

Secondary currents on CT secondary windings must not beallowed to reach levels which may burn out wiring and/or

meters.




Stn. Service Metering700:5

(140:1)

Ifault = 286A

Istn service = 14 mA

Igen = 21.4 A

Gen. Metering3000:5

(600:1)

Ifault = 67A

Igen = 5A

Limitations of Conventional Technology

Constraints for choosing CT ratio:

Ifault < 300A for 1 cycle

Igen < 15A continuous.Istn service > 5% of Igen


13.8 kV

Stn. Service Xfmr.

475 kW load



225 MVA

13.8 kV, 60 Hz

Design Constraints at 138 kV:

Fault Level = 40 kA

Max. Gen. Current = 3000A

Stn. Service Load = 2A

Stn. service metering cannot be achieved

with conventional CTs due to range andfault levels!



Yes, but with its own problems.

Multiple metering points could be installed on low side, but:

• Requires utility equipment on customer premises. (may notbe desirable)

Can the Problem be Overcome Using Conventional Technology?

• Metering at generation bus may be more expensive due to:

- isolated phase bus

- high currents at generation bus

- station service load would have to be “split off” fromgeneration when the generators are on to prevent charges to

IPP

• Transformer losses may require estimation.



Does the problem warrant attention?

Why not estimate the station service load?

• Station service loading consumes energy which has value.

• Estimation of station service load is not accurate.

• Actual measurement will prevent disputes between IPP and utility.

It isn’t much power being used, but it is a load which is always there!

• 475 kVA stn. service (8000 hrs) vs 700 MVA generation (900 hrs)



Benefits of Metering Using Optical Transducers

• Single metering can be installed at “point of sale”.

-no estimations of loads or losses

-installation on utility premises

• Insensitive to high fault levels.

• Accurate over entire dynamic range.




Optical Current Sensing Solution

Analogue Meter

(Analogue Metering)

120V analoguesignal

Current Sensor

Voltage Sensor

NXVCT

1A analoguesignal


13.8 kV

Stn. Service Xfmr.

475 kW load



225 MVA

13.8 kV, 60 Hz

Optical CurrentElectronics

DAC,Amplifier

Optical VoltageElectronics

DAC,Amplifier

- 0.2% accuracy over 2 – 3000A range



Optical Current Sensing Solution

Meter with digitalinput

(Digital Metering)

Current Sensor

Voltage Sensor

NXVCT

Optical CurrentElectronics

Optical VoltageElectronics


13.8 kV

Stn. Service Xfmr.

475 kW load



225 MVA

13.8 kV, 60 Hz


MergingUnit

- 0.2% accuracy over 2 – 3000A range

- Analogue, digital conversions removed



Optical current sensing can provide cost effective

solutions to metering (and protection) problems thatcannot be easily solved using conventional technology.

Future progress into a complete digital system willprovide additional benefits that will exceed thecapability of analogue systems.



Questions?

James Hrabliuk, P. Eng.

NxtPhase Corporation

3040 East Broadway

Vancouver BC V5M 1Z4

[email protected]

www.nxtphase.com

604-215-9822 ext 243

UPS D9-11 1 Optical Design Options Nxt Phase

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