Name: Abdullah Al Ghamdi Company: GCCIA Position: Head of …

Name: Abdullah Al Ghamdi Company: GCCIA Position: Head of HVDC

The GCC Interconnection Project

Connects six countries with 400 and 220KV links

GCC NETWORK & Objectives

Ensure Power System stability

Reduce overall Spinning Reserve

Reduce Installed Capacity

Requirement for Reserves

Support during Blackout

Energy Trading

*

3 x 600 mw Al-fadhili btb hvdc converter

GCCIA HVDC Back-to-Back CONVERTER FACILITY

AC Voltages / Frequency: 400 kV (50 Hz) / 380 kV (60 Hz)

Rated Power : 3x616 MW @ 55C ambient temp.

Valves COOLING: De-Ionized Water Cooled

Thyristor Triggering: Electrically Triggered

Converter Transformers 50Hz: 380MVA

Converter Transformers 60Hz: 385 MVA

HVDC operational Setup

HVDC Back-to-Back station consists of three poles with 600 MW for each

HVDC has modes of operations

Dynamic Reserve Power Sharing (DRPS) mode

Economic Power Dispatch (EPD) mode

The DC links are initially in standby mode or transferring power (EPD)

Supply of reserve power is done automatically by the HVDC control system

HVDC can be remote controlled from ICC or locally

Valve Hall

HVDC Converter Transformers

Switchyard

HVDC BACK-TO-BACK CONVERTERS FACILITY

HVDC Functions

To interconnect the 50Hz and 60Hz systems

To provide reserve power sharing

To stabilize the interconnected systems following a critical loss

of generation

To permit up to 1200MW of economic active power transfer between the

member states

HVDC modes of operations

HVDC

modes

Hot Standby

Mode

The Poles are kept

energized from the AC

(50Hz and 60Hz) grid,

with no power transfer i.e. poles in the

blocked mode

Dynamic Reserve Power Sharing (DRPS)

Mode

Power transfer is activated

automatically when pre-defined criteria is met to

assist in achieving dynamic

stability in either the 50Hz

or 60Hz systems.

60 events since 2009

Economic Transfer (ET)

Mode

Frequency Control (FC)

Mode

Up to 1200MW of active power

transfers between 50 Hz

and 60Hz systems can be scheduled and implemented

The Triggering Criteria enables

operating reserve sharing between

both blocks following the N-1

loss of generation or demand within

either system. 21 events O/F 99 EVENTS U/F

Total FC events 120 SINCE 2015

When df/dt >0.1hZ /s

After 500ms the power

requirement is at least

240MW(0.39pu)

Now the soonest that

the pole will be de-

blocked is after 550ms

from an event.

Will Deblock to

between 240MW and

550MW

DRPS Triggering Criteria STAGE-1

10

fo

F

HVDC acts automatically when frequency drop below

frequency dead band ∆ F for specific time t

Power contributions for any

deviations is calculated based on two

different power/frequency slope

characteristics on either side

HVDC support

Frequency Control

11

FC

Operation & maintenance challenges

Because of the climatic and environmental conditions in the

Kingdom of Saudi Arabia where HVDC is located, the extreme

and daily seasonal variations in temperature and high level of

pollution from sand and dust has impact on the following:

Control and Protection

Valve Cooling System

Valve hall Component failure

Outdoor Switchyard equipment


Control & Protection

• Interlocks signals causing pole to become not ready for service

• dust contamination inside panels because there is no dust filter on the control panels and no bag filters on HVAC

• Maintenance procedure and intervals have been changed to clean racks dust filter monthly and replace them yearly


Control & Protection

• Other common control and protection challenge is the obsolescence of spare parts

• Processor cards became obsolete in 2013

0

1

2

2011 2012 2013 2014 2015 2016 2017 2018

Power supply module Sharc Processor Card Pentium Processor Card Change over unit Analogue card Media Converter

C&P Components Failure Statistics

Valve Cooling (VC) System challenges


Valve cooling system few Protection philosophies as following,

Inlet coolant temperature Protection

Valve coolant inlet temp low alarm : 15° C

Valve coolant inlet temp low Trip : 5° C

Coolant Condensation

Valve coolant inlet temp – valve hall dew point temp ≤ 5° C “Valve cooling condensation risk” minor alarm will be triggered.

Valve coolant inlet temp – valve hall dew point temp ≤ 2° C “Valve cooling condensation danger” major alarm and will initiate blocking of poles and tripping of converter transformer & filter CB’s.

Control measures for condensation


Temperature controlled shunt valves are installed to

prevent passage of coolant during low temperatures

Shunt valve & bypass valve operated using PID

controller for the inlet temperature of 30°C

15% Mono Ethylene glycol is added to avoid coolant

freezing in outdoor coolers.

Before (Without Shunt Valve) Current (With Shunt Valve) Detailed view of Shunt Valve

VC Emergency Backup support

440V, 150 Ah VRLA battery bank is integrated with the VC

system. Battery bank supports the main pump, by feeding VFD

DC bus, during the temporary auxiliary power supply

interruptions.

Back up system supports the pump for 45 sec by switching the

pump to Low speed. If interruption exceeds 45sec tripping

command will be initiated.

Short cycling of the battery bank, because of intermittent ATS,

bank resulted in under voltage protection operation in UMD

that feeds the cooler fan of main VFD.

Control measures

Battery banks were replaced in year 2016

LVAC ATS scheme is revised



Valve Hall Components Failure statistics

Valve hall comprises 50 & 60 HZ converters in quadrilateral arrangement. Fundamental building block of converter is called Thyristor Clamped Assembly (TCA). TCA is equipped with di/dt reactor, Thyristor & it’s associated Gate drive units (Gate, divider card). Following figures depicts various element failure for 9 years,

Avg. annual failure rate for Thyristor = 0.1 %

Avg. annual failure rate for Gate card = 0.11%

Avg. annual failure rate for Divider card = 0.05%

Valve Hall Annual Preventive maintenance is covering two quadrivalves in one converter station, one on the 50Hz & another one on 60Hz side in a calendar year.

0

5

10

15

20

10

20

11

20

12

20

13

20

14

20

15

20

16

20

17

3 1 2 2

10

1 1 3 3 2 3

1 1 3

1 2

15

Co

un

t

Year

Thyristor & Card Failures

Gate card

Divider Card

Thyristor

0

1

2

3

4

20

10

20

11

20

12

20

13

20

14

20

15

20

16

20

17

1 1

2

1

2

3

4

1

2

Co

un

t

Year

Coolant Leak &di/dt reactor

di/dt reactor

Coolant leaks

GRP strap Failure

Coolant leaks & Detector

Two numbers of coolant leak detector is mounted at the bottom

of corona stress shield per Quadrivalve. Coolant leak in any

levels will be guided to bottom tray & collected in coolant leak

detector bucket. Bucket tips when filled with coolant (Approx.

100 Cm3).Fibre Optic senses bucket movement & relaying

bucket status to Valve Based Electronics (VBE).

Protection logic in Fadhili HVDC as follows,

Minor coolant leak Alarm- Bucket decants & returns to normal

position in less than 3 Seconds

Major coolant leak Trip- Bucket in decant position

continuously for more than 3 Sec (or) decants two times within

3 minutes.

Bottom Tray

Coolant Bucket


Coolant leak variants

di/dt Reactor connection

Drain Olive bloc

Isolation valve

Thyristor heat sink connection


Coolant leak Failure modes

Cracks on the fittings

Damaged ‘O’ rings

No other known failure modes.

Operational experience suggest that Low

temperatures coolant & thermal

expansions when the pole are DE blocked.


Leak Detector issues

Coolant leak detector bucket stuck-up during the

operation.

Rotating shaft support block clearance getting

affected by moisture absorption.



Switchyard component failure

0

2

4

6

8

10

2011 2012 2013 2014 2015 2016

3

9

4 3

0

4

Year

Harmonic Filter Capacitor Failure

Pole-1

Pole-2

Pole-3

Total

22, 54%

19, 46%

Capacitor Failure Mode

Capacitancedeviation

Oil leak

Capacitor oil leak attributed

to climate factor

Annual Average Harmonic filter capacitor failure is 0.06 %

0

2

4

6

0

4

0

6

3

5

Year

PLC Filter Capacitor Failure

50Hz PLC

60Hz PLC

PLC total

Annual Average PLC filter capacitor failure is 0.83 %



Capacitor failure on 18.05.2019 nine capacitors were damaged and replaced

Recommendation:

Improve the design with fused type

capacitors.

Check the feasibility study for filter

switching improvement by Point-on-

Wave relay wherein the Circuit Breaker

of each phase of the harmonic filter

should close at an instant near the

voltage zero crossing.

Check the possibility of improving

temperature detection/protection system

P2_EDC_501_2019-05-18_12h16min15s000ms_2 - Copy.avi



Burned PLC reactor due to bird’s nest

Mitigating measure: Bird’s spikes were

installed on top of the reactor

Cat’s intrusion to

energized equipment

caused short circuit

Mitigating measure:

barbed wire were

installed on the fence

and sealed the gap b/w

the ground and the fence


Adverse weather condition: Sandstorm

Regular cleaning/sand removal being done

380kV Cable joint & SVL failures

Random SVL failures occurred for 380kV & 400kV Cable

circuits. Failures statistics shown in below table,

- No apparent fault conditions reported within HVDC

- No Switching/Lighting surges recorded by Surge arrester

counter in the cable sealing ends.

In Nov 2017 380kV cable joint failure occurred

Root cause analysis is being conducted for SVL failures and

proposal to implement PD monitoring for cable circuits.


Period Pole-1 Pole-2 Pole-3

Nov 2015 –

May 2019

Nil 50Hz- Nil

60 Hz- 3 Nos

50Hz- 1

60 Hz- 3 Nos


Availability and Reliability

0

20

40

60

80

100 87.3

9

62.0

0 88.4

3

75.1

6

77.6

9

95.0

4

97.6

8

98.1

6

95.3

0

Energy Availability %

0

5

10

15

20

20

09

20

10

20

11

20

12

20

13

20

14

20

15

20

16

20

17

FOFI

Energy Availability of Al Fadhili HVDC Force Outage Frequency Index (FOFI)

Factors affecting the Reliability and Availability

-Oman HVDC Link

-Iraq HVDC link

-Upgrade of HVDC Control System

-Enhancement of power transfer from 1320 MW to 1980 MW

Future Plans

Conclusion

Most of the challenges on Al Fadhili HVDC project are related

to the unique design and operation on the facility being on

hot standby mode.

Despite of the challenges faced during the 10 years of

operations of HVDC it can still attain a high level of Energy

Availability and Reliability

Thank You

Abdullah Al Ghamdi- Head of HVDC

Email : [email protected]

GCCIA www.gccia.com.sa

Saudi Arabia- Dammam

mailto:[email protected]

http://www.gccia.com.sa/

Documents

Name: Abdullah Al Ghamdi Company: GCCIA Position: Head of …