Solving Old Problems with New Technology - Monitor and

Measure GIC and OPD Currents

Marcelo Zapella, Lucas Oliveira, Rich Hunt , Dylan StewartGE Grid Solutions

Presenter: Mark Adamiak – GE Grid Solutions

2018 Texas A&M Protective Relaying Conference

Summary

• Introduction to problems: GIC and OPD

• Optical CT principles and IEC 61850-9-2LE devices

• How to monitor and measure GIC

• How to monitor and measure OPD, including field tests

Introduction:Geomagnetic Induced Currents• Solar storms generate coronal mass ejection, affecting the

Earth’s magnetic filed, causing electrical currents

• Quasi DC currents, in the order of tens to hundreds amps

Introduction:Geomagnetic Induced Currents• On March 1989, the province of Quebec in Canada

experienced severe geomagnetic storm causing a collapse in the Hydro- Québec power grid

• The protective relays tripped in a cascading sequence of events, leaving more than six million people without power for hours, with significant economic loss

Introduction:Open Phase Detection• Open Phase Detection (OPD) is a sensitive subject to nuclear

industry worldwide

• An undetected open phase can compromise the availability of plant auxiliary systems

• A reliable and accurate open phase detection system is mandatory

• An open phase detection system (OPD) can be constructed using various elements of a digita l substation

Introduction:Open Phase Detection• Diagram illustra tes concern with an open phase on one of the

connections to primary windings of a sta tion auxiliary transformer (SAT)

Primary Voltage

Magnetization Current

Introduction:Transformer Magnetizing Current

Optical Current Transformer (OCT)Magnetic-Optical Phenomenon• Faraday’s effect: interaction between a magnetic field and the

light – or the rotation of polarized light

• The Faraday’s effect does not depend on the varia tion of the magnetic field over time, thus the sensor is susceptive to DC currents as well as AC

• Rotation is linearly proportional to the current flowing in the conductor

IEC 61850-9-2LEDFRs and Protective Relays• Analog current and voltage measurements are digita lized in

sampled values (SV)

• Streaming of sampled values (each stream has 4 analog signals)

• Enables differently optimized architectures for distributing their data to other devices

Geomagnetic Inducted-Currents (GICs)How to Monitor and Measure?• Optical CT electronics receives the raw optical signals from

the sensing rings

• Individual phase/neutral currents > sampled values

• Once a DC level threshold is crossed the DFR registers COMTRADE waveforms (including DC offset and harmonics

Open Phase Detection (OPD)How to Monitor and Measure?

Open Phase Detection (OPD)How to Monitor and Measure?• Unloaded power transformer draws

unbalanced high-side magnetization current in each phase of 50 to 1000 mA with significant harmonic content

• A digita l relay is used to a larm condition which corresponds to the open phase, the DFR registers the current waveforms and sequence of events

• A VT triggered digita l comb filter is applied to optical CT digita l data to extract the fundamental and harmonic components to a few mA

Open Phase Detection (OPD)Field Test Results• Unloaded wye-wye transformer:

Phase A, B and C connected

+90°

-90°

±180° 0°

300.0 kV800.0 mA

V_AI_N

I_C

I_B

I_A

±

8

Open Phase Detection (OPD)Field Test Results• Unloaded wye-wye transformer:

Phase A and B connected; C open

+90°

-90°

±180° 0°

300.0 kV3.0 A

V_A

I_N

I_C

I_BI_A

Open Phase Detection (OPD)Field Test Results• Unloaded wye-wye transformer:

Phase A connected; B and C open

+90°

-90°

±180° 0°

300.0 kV1.0 A

V_A

I_N

I_CI_B

I_A

±

1

Open Phase Detection (OPD)Field Test Fiber Optic CT• Slip-on fiber optic CT over high-side transformer bushing used

to detect open phase condition

Open Phase Detection (OPD)Field Test Cabinet• Trip indication and relay voting

indication

• IEC 61850-9.2LE relays

• Target reset switch

• IEC 61850-9.2LE digita l fault recorder

• Optical CT merging units

• Power breakers

Conclusions

• Use of optical CTs allow solutions to industry issues (GIC, OPD)

• Relay logic for different applications

• DFR for monitoring and recording

• GIC scheme is a proposition for monitoring and measuring

• OPD Scheme has been proven to be applicable to:• Various load conditions• Wye-Wye, Delta-Wye, and Wye-Delta transformers

including shell and core form construction

Thank You

Questions?