1. RfG – Fast Fault Current Injection Update
Antony Johnson / Peter Simango
National Grid – Network Capability
March 2017

2. Disclaimer
Note this presentation covers the study work completed to date in respect of evaluating the requirements for fast fault current injection.
A test network has been set up and the models tested.
A multi machine study has also been set up and initial studies started however these need to be completed before results and conclusions can be drawn
Stakeholders are therefore requested to be aware that such analysis does take time and the results presented in this presentation reflect a snap shot of the work completed to date.
A further update with a more complete set of results will therefore be provided at the April meeting.

3. Summary Test Network and proof of concepts
Test Network Performance – Synchronous Machines
Test Network Performance – Power Park Modules
Variations in Converter based reactive current injection
Virtual Synchronous Machine
Multi Machine Study
Set up and initial work completed to date.
Summary / Next Steps

4. Test Network( Fig1)

5. Test Network Behaviour of Synchronous Plant
Assumptions
A three phase fault was applied at 400kV Ref Bus
The fault infeed at 400kV Ref Bus was taken as 10000MVA
Synchronous plant varied at the 33kV busbar varied from 1MVA – 50MVA
The same starting point was assumed for asynchronous plant

6. Test Network - Results Behaviour of Synchronous Plant (1MVA)

7. Test Network - Results Behaviour of Synchronous Plant (25MVA Group)

8. Test Network - Results Behaviour of Synchronous Plant (50MVA Group)

9. Test Network – Synchronous Plant Summary of Results
To achieve a minimum retained voltage of 10% at the 33kV busbar, at least 25MVA of synchronous plant is required at the 33kV busbar
The current injection from this group of synchronous plant synchronous plant is approximately 4.3pu
The retained voltage at 33kV is around 12% during fault conditions
The greater the number of machines the higher the retained voltage on the 33kV busbar

10. Test Network Behaviour of Power Park Modules
Assumptions
The same number (rating) of Power Park Modules as synchronous machines was used
The Asynchronous machine was modelled as a static generator with Phase Locked Loop (PLL) control
Standard Power Factory Static Generator model applied
The blocking voltage varied between 10% and zero
Voltage and current injection plots obtained

11. Test Network - Results Behaviour of Power Park Modules (Switching threshold = 0.1pu)

12. Test Network - Results Behaviour of Power Park Modules (Switching threshold of =0) (25MVA)

13. Power Park Modules – Reactive Current Injection
Reactive Current (p.u)
Static Generator
Max Value
Ramp Rate
Time Delay
Time (ms)

14. Static Generator Parameters

15. Test Network - Results Power Park Modules (Max 1
Test Network - Results Power Park Modules (Max 1.5pu injection 25MVA group)

16. Test Network - Results Power Park Modules (Max 1
Test Network - Results Power Park Modules (Max 1.5pu injection 50MVA group)

17. Test Network - Results Power Park Modules (Max 1
Test Network - Results Power Park Modules (Max 1.5 injection 100MVA group)

18. Test Network – Static Generator with Fast fault current injection
The more the machines the better the terminal voltage
It is possible to delay the injection
The higher the injection the less the number of machines required to achieve the desired retained voltage
For Power Park Modules the maximum reactive current injection (eg 1.5pu) is critical
Max Current Injection (pu)
1.5
No of Synchonous machines (1MVA each ) 1 25 50
100
33kV Retained Connection Voltage[pu]
0.043
.0.833
0.17

19. Test Network Comparison for the three cases
No of machines (1MVA each ) 1 25 50
100
Static Generator Retained Connection Point Voltage
0.011
0.023
0.033
Sync. machine retained Connection Point Voltage
0.13
0.24
0.38
Stat. Gen With FFCI retained Connection Point Voltage
0.043
0.0833
0.17
When the number of Power Park Modules is very low the fault current contribution is insignificant
A group of synchronous machines will offer significantly more voltage support compared to the same number Power Park Modules

20. Test Network - Results VSM Model
The network is the same as that shown in Figure 1
VSM technology uses the same static generator but the controller has been modified to reflect VSM capabilities

21. Test Network - Results VSM 25MVA

22. Test Network - Results VSM 50MVA

23. Test Network - Results VSM 100MVA

24. Test Network – VSM Performance
The more the machines the better the retained Connection Point voltage
The VSM offers slightly better performance than a standard PPM Converter using PLL
VSM Size 25 50
100
33kV Retained Connection Point Voltage[pu]
.0035
0.071
0.141

25. Multi Machine Study approach and Methodology
Full GB Transmission Network
Includes DNO Networks
Specific area of interest will focus on an area of the network known to have a high volume of Embedded Generation: South West
Base case study
Intact network conditions
System conditions – Max / Min Demand
All embedded generation initially modelled as negative demand
Solid Three phase short circuit fault applied at various points across the South Western part of the Transmission System
Voltage profile assessed across the Transmission System and DNO system during and after the above faults

26. Area Under Study

27. Multi Machine System Study Assumptions Demand as negative Gen Base Case
Fault Condition: Solid Three phase double circuit fault between Indian Queens and Taunton substation

28. GB System Study Embedded Generation modelled as Negative Demand
The Voltage at the point of fault on the Transmission System is zero
A number of busbars have a voltage above 10% due to network interconnection
The voltage at Hayle 33kV busbar is 0.012pu.

29. GB System Study Result Summary Embedded Generator modelled as 25MVA synchronous machine )

30. GB System Study Result Summary Embedded Generation modelled as 25MVA synchronous machine
The Voltage at the point of fault on the Transmission System is zero
The Connection Point Voltage at Hayle 33 kV Substation has increased from 0.012pu to 0.163pu
This improvement has cascaded to some of the busbars around the network

31. GB System Study - Results (Embedded Gen Modelled as static Gen)

32. GB System Study - Summary Embedded Generation modelled as 25MVA Static generator
The Voltage at the point of fault on the Transmission System is zero
The Connection Point Voltage at Hayle 33kV substation has increased from 0.012pu to 0.051pu

33. Multi Machine System Studies Progress to Date
Case 1 Base Case with Embedded Synchronous Generation explicitly modelled in DNO network and specific transmission faults applied. – Ongoing
Case 2 Base Case with Embedded Power Park Modules explicitly modelled in DNO Network and specific transmission faults applied - Ongoing
Case 2A As per case 2 with variations in reactive current performance – To be completed
Case 2B As per case 2 but the converters installed within the Power Park Modules are modelled with Virtual Synchronous Machine (VSM) capability - To be completed

34. Summary / Next Steps
Test network setup to test machine and controller models
Multi machine network set up and studies ongoing
It is too early to draw any concrete conclusions
Initial results would indicate that low fault current, particularly from Converter based plant provides little voltage support during Transmission System faults
The greater the volume of Embedded Generation the higher the retained voltage
Distribution and volume of Embedded Generation at this stage would appear to be a significant factor in determining the parameters for fast fault current injection and voltage against time curves.
A further update will be provided at the next meeting in April