The challenge to approve grid compliance

Brandon Peterson

Date 8 August 2017

Contents

• Grid Code requirements

• RPP and NSP obligations

• Examples

2

Grid Code requirements

• Power Quality requirements indicated in RPP Code Ver 2.9, Clause 9 and Annexure 13

• ≤ 5 MVA only require compliance certificates to prove compliance

• > 5 MVA must prove compliance as per code.

• Utility obligations as per the code

• To provide limits for the PQ parameters (apportionment)

• RPP obligations as per the code

• Prove compliance to limits via measurement and not simulation

• Prove that RPP is not exceeding the 3 x Zh ceiling

3

RPP obligations

• Use a IEC 61000-4-30 class A compliant device to prove compliance.

• Compliance must be proven at the Point of Connection

• Measurement for minimum of 7 days

• Measure both voltage and current

• Power output of plant must be representative of expected output.

• Compliance must be under all network conditions

• Measure on the MV side in the case of voltage flicker and voltage unbalance.

• Compliance must be proven within 2 months of Commercial Operation date.

8 August 2017 4

RPP obligations continued

• Appendix 13 = Guideline on how to prove compliance – no deviations allowed

• Main compliance is proven via the current measurements.

• Pre and Post measurements not allowed for grid code compliance.

• No provision made for it in the guideline (Law).

• Conditions under which measurement are taken not consistent

• No or low power output is not considered to be pre measurement condition.

• CIGRE technical report 468 used for compliance methods

• Constraint =10 min aggregated rms value

• Difficult to prove direction of harmonic emission.

5

Simple emission theory

6

Ih

Eh0

Vh

Ehc

Problem with Scalar values

7

Vh

Eh0

Ehc

Eh0

Vh

Ehc

Harmonics being generated

Harmonics being absorbed

Problem, scalar values will is a magnitude only.

Without the angle it is difficult to say if it the emission is absorbed or generated.

Utility (NSP) expectation

• RPP to take into account PQ requirements at design stage

• Often taken into account only at the END.

• RPP are encouraged to engage with NSP regarding any potential problems that may be foreseen

• RPP’s are not taking advantage of this hence delays in the compliance process

• A detailed report to be sent to NSP

• Measurement (how, when, where, etc.)

• Assessment method employed as per Grid Code guideline

• Compliance to 3 x Zh (often left out of report)

8

Utility (NSP) Challenges

• Proving that the RPP is “absorbing” or “emitting” the pollution

• Statistical method (CIGRE 468)

• Not always conclusive

• Corresponding change in voltage and current for harmonics

• Qualitative analysis

• Once direction is “proven”, tendency is to assume same behavior 24/7

• Compliance is proven at an instance in time

• Network configuration changes (taken into account by NSP)

• Impact of adjacent RPP’s

9

Examples of scatter plots

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0

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0 0.5 1 1.5 2 2.5

5th

ha

rm

on

ic v

olt

ag

e [

V]

5th harmonic current [A]

5th Voltage and Current scatter plot

5th scatter

Zh

Zhc

2nd harmonic correlation – Site is generating

11

3rd harmonic correlation – Site is absorbing

12

Utility (NSP) Challenges

• Inconsistent approaches by RPP consultants

• Report formats

• Assessment methods (some within and others outside of Grid Code)

• Turn around time of reports

• NSP not just focusing on RPP Grid Code compliance.

13

Conclusion