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Compliance of Solar PV Installation with the

New Renewables SA Grid Code

Jimmy Goulding, Electrical Technologist, Aurecon,

South Africa

Content

Introduction

Overview of Categories for Grid Connection of

Renewable Power Generation

Technical Considerations

Current Legal Requirement and Exemption

Process

Conclusions

Introduction

The primary objective of the recently released

Grid Connection Code for Renewable Power

Plants (RPP’s) grid connection code is:

− To specify minimum technical and design grid

connection requirements for Renewable

Power Plants (RPPs) connected to or seeking

connection to the South African electricity

transmission system (TS) or distribution

system (DS).

Introduction (continued)

A summary of the those technical requirements

as stipulated in the this code is relevant to all

forms of renewable power

If any specific requirements are relevant to PV

only this is identified

The technical requirements identified need to be

noted by the developers and manufacturers for

design purposes

There is a process for application for exemption

from requirements which needs to be followed

Introduction (continued)

This presentation simply identifies selected

technical requirements in the RPP code that are

considered to be the most challenging and

hence need careful consideration

This latest version of the RPP Connection Code

is a document that the System Operator will

gladly discuss and debate specific queries

Categories for Grid Connection

of RPP Generation

There are three Categories which are derived

from the voltage connection level and proposed

installed capacity:

− Category A: Small or Micro Turbines

connected to LV levels having a

size of less than 1MVA. (LV –

voltages up to and including 1kV)

.

Categories for Grid Connection

of RPP Generation (continued) − Category A is further split into three sub

categories:

− Category A1: 0 - 13,8kVA

− Category A2: 13,8 - 100kVA

− Category A3: 100 – 1MVA

− Category B: 1MVA-20MVA and generators

less than 1MVA connected to the

MV System. (MV - 1kV up to and

including 33kV)

− Category C: 20MVA or higher


Looking at those technical requirements that need

to be noted by the developers:

Section 5.1 - Tolerance of Frequency and

Voltage Deviations – Normal Operating

Conditions

− Voltage Ranges - ensure compliance as

specified, however this is not in line with NRS

048-2 and the SA Transmission Network Code

− Amendment to the voltage ranges has been

requested


(continued)

− Frequency Ranges - ensure compliance as

specified

− These frequency operating ranges are in line

with International practice

Section 5.2 - Tolerance of Frequency and

Voltage Deviations – Abnormal Operating

Conditions

− Clause 1 – Phase jump ride through at the

point of connection (POC)


(continued)

− Network faults, specifically short circuit type)

can cause phase jumps larger than the 40

phase jump specified in the RPP code

− Does this mean disconnection of the

generators if above 40 phase shift even

within the Low Voltage Ride Through limits?

− This question has been raised and

consideration is being given to limit this

requirement between the normal operating

voltage range only as specified in the RPP

code


(continued)

Section 5.2.1 - Tolerance to Sudden Voltage

Drops and Peaks – Abnormal Operating

Conditions

− The Low Voltage and High Voltage Ride

Through (LVRT and HVRT) requirements are

illustrated in the RPP code for all categories at

the point of connection (POC)

− Category A1 and A2, LVRT only – at present is

questionable - present proposed penetration

levels of RPP into the South African Grid are

extremely low


(continued)

− Due to these generators connection at LV

levels – impact of localised voltage dips due to

faults on the network would generally not lead

to disconnection of these small plants

− Even in the case that they do disconnect – the

impact to the security of SA Grid would not be

compromised

− This requirement for the Category A1 and A2

has been queried – either to drop it or

postpone until higher penetration levels RPP

are reached in South Africa


(continued)

− LVRT and HVRT requirements for categories

A3, B and C are defined at the point of

connection (POC)

− Besides staying connected in these defined

voltage limits there is a requirement for these

RPP’s to deliver reactive current in the case

that the voltage is outside the normal

operating band

− WRT A3 and B

− LVRT is technically feasible for inverter-

driven generators – although demanding


(continued)

− HVRT requirement is of concern for many

inverters due to well defined maximum

voltage limits

− Due to the same reasons as mentioned in

Category A1 and A2, the low penetration

levels of RPP, these voltage increases of

short duration would not be expected over

the whole system

− Hence, query raised to consider

postponement of this requirement until

penetration levels are higher


(continued)

− WRT reactive current support for A3 and C

generators – benefit is questionable – what

is the advantage since this is typically to

support voltage dips in a system with a large

penetration of inverter-driven generators?

− Low voltage support at MV and LV levels

where the electrical protection generally non

directional – and the fault levels low- tripping

selectivity is difficult and incorrect tripping

can result

− Hence system stability can be compromised


(continued)

− The RPP code at present does not allow for

disabling of reactive current injection by the

System Operator

− Query raised to consider that A3 inverter-

driven generators be exempt from providing

reactive current support and allow selectivity

of reactive current injection for inverter-

driven generators of Category B

− WRT Category C

− LVRT and HVRT is technically feasible for

inverter-driven generators - demanding


(continued)

− WRT reactive current support for these

generators – the requirement is supported,

however, this support requires fast control

− The RPP Code defines that this support

should be at the point of common coupling

(PCC) within specific time intervals

would require fast control – this may be

challenging when considering a large

amount of central inverters and

communication to and from these


(continued) − Query raised that this control requirement

be at the individual inverters on the LV

Terminals instead of at the PCC, with a

slightly relaxed settling times

− Query raised that incremental reactive

current limits be used instead of limiting total

current and if the reactive current definition

at the POC was to remain it would require

that the absolute value of voltage should be

replaced by a voltage change - both these

as shown on the characteristic the RPP

code.


(continued) Section 6 – Frequency Response

− WRT Category A – Requirement is for power

curtailment for over frequency conditions - in

line with international standards and most PV

inverter manufacturers should be able to

adjust their equipment to meet the SA

requirements

− WRT Category B and C – Requirements are

for primary frequency control for over and

underfrequency conditions as shown in the

RPP code


(continued)

− WRT Category B and C

− Requirements are for primary frequency

control for over and underfrequency

conditions as shown in the RPP code

− This functionality is only required if a

specific agreement is made with the System

Operator for this capability

− Internationally this requirement is generally

not required from RPP’s


(continued)

− This frequency support functionality is

assumed to be required during emergency

conditions

− Hence, a query was made again

addressing the case that the RPP’s initial

penetration into the grid is of such a low

amount, how much influence would these

utilities have under these conditions?


(continued)

− A query also made that perhaps category B

and C generators should have the same

requirements high frequency response as

Category A as a mandatory requirement

− A query also made that Category B and C

generators need only consider the other

frequency requirements if a specific

agreement with the System Operator was

desired


(continued)

Section 7 – Reactive Power Capability

− Generally speaking, these requirements are in

line with international standards

− Suggestions made that Category A1 and A2

generators should operate at unity power

factor with a tolerance band specified and A3

generators operating in the range of 0.95

leading/lagging power factor


(continued)

Section 8 – Reactive Power and Voltage Control

− These requirements are clear and concise

− Dynamic control requirements – not specific

− Suggestion made that a clear statement on

the dynamic controller requirements for the

use and application of Mechanically Switched

Capacitors and Reactors (MSC’s and MSR’s)

to comply with the reactive power

requirements needs to be made

Conclusions

Development of this RPP code in a short time so

as to accommodate the intended RPP’s

connection into the SA Grid - therefore there will

be amendments to bring requirements not in line

with international requirements into line without

compromising the security of the existing system

Static and Dynamic Studies by developers and

manufacturers are essential to ensure correct

design and engineering

There are other requirements not mentioned

here, however these covered are the ones

providing the most concern at present.

Current Legal Requirement and

Exemption Process The question was posed to the System Operator

and NERSA with regards to the requirements

until the revised version is published – The

existing version 2.6 is the current legal

document

Hence, if there is a compliance issue of a

temporary nature – manufacturers / developers

will need to apply for temporary exemptions

The same applies for permanent non

compliance – application for this will need to be

made

For any additional information, please do not

hesitate to contact Jimmy Goulding:

Email: [email protected]

Phone: +27 21 526 6996

Aurecon SA (Pty) Ltd

Thank you

Contact Details

mailto:[email protected]

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