Rennie Executive Director Matt Rennie sat down with Naveen Rajagopal from Rennie’s Grid Connections team to discuss when developers should start thinking about grid connection, how early-stage feasibility should shape project design, and why Australia’s increasingly complex power system is changing the role of the grid engineer.

Australia’s energy transition is making grid connection one of the defining challenges for renewable energy and storage development.

The NEM is absorbing increasing volumes of inverter-based generation and storage, parts of the network can operate under relatively weak system conditions, and developers are pursuing larger and increasingly sophisticated BESS and hybrid projects. At the same time, development teams are being asked to make decisions about land, project size, technology and investment before every aspect of the connection solution is known.

Matt Rennie spoke with Naveen Rajagopal from Rennie’s Grid Connections team about what developers should be doing differently — and why the best time to discover a grid problem is while you still have choices.

Matt Rennie: When a developer first calls you, where are they normally in the development process?

Naveen: It varies, but ideally we become involved quite early. Often the developer has identified a site and is working through the land or lease arrangements. They may know they want to develop a wind farm, solar farm or BESS, but the optimal capacity and connection configuration are not yet fixed.

That is actually a very useful time for us to become involved because the developer still has options.

Our first task will often be a grid feasibility study. At that stage, we’re not trying to complete the connection application. We’re trying to establish the technical envelope within which the project can sensibly be developed.

We want to understand the proposed connection point, the characteristics of the surrounding network and the amount of generation or load that can potentially be accommodated. From there, we can test different project sizes and operating conditions.

For me, the important principle is that grid feasibility should help shape the project rather than simply validate a project that has already been designed.

Matt Rennie: What does a Grid Connections feasibility study actually examine?

Naveen: We start by understanding the existing network and proposed point of connection.

We then undertake power-system studies to identify potential limitations. That can include thermal loading of transmission lines and transformers, voltage performance, reactive-power requirements, system-strength considerations and other network constraints that may affect the project. We also assess the feasibility of connection points – a nearby substation, LILO arrangement in an existing transmission corridor or the requirement for DNA.

We also need to think about the network dynamically rather than just looking at today’s configuration. What augmentations are planned? What other generation, storage or load is expected to connect in that part of the network? How might different dispatch conditions affect the project?

If a developer says, for example, “We have enough land for a 240 MW project”, I don’t necessarily want to model only 240 MW. We might test 120 MW, 160 MW, 200 MW and 240 MW in steps to understand the impact on the network.

We can then test different operating points – 25%, 50%, 75% and 100% output – under different network and seasonal conditions.

For a BESS, you need to consider both directions because the plant operates as both load and generation. Maximum charging can create a very different network condition from maximum discharging.

So, the answer we give the developer should be much more useful than simply saying, “Yes, this project can connect,” or “No, it can’t.” We want to explain where the technical boundaries appear to be, what is driving them and what options the developer has.

Matt Rennie: How much work is required before you can give a developer confidence that there isn’t an obvious connection red flag?

Naveen: A typical feasibility assessment might take four to six weeks, depending on the complexity of the project and quality of the information available.

We collect the relevant network and market information, understand existing and proposed network developments, build or adapt the required power-system models and then run the project across a range of scenarios.

An important distinction is that feasibility isn’t intended to replicate every study that will eventually be required through the formal connection process. That would be unnecessarily expensive at such an early stage.

What we want is enough engineering rigour to identify the material risks.

If there is likely to be a significant thermal constraint, voltage issue or system-strength challenge, the developer needs to know that before committing to a project configuration on the assumption that connection will be straightforward.

Likewise, if moving from 200 MW to 300 MW produces disproportionately greater network issues, that is extremely valuable development information. There may be a technically and commercially better project at 200 MW.

The developer can then take our technical analysis and combine it with market modelling and financial analysis to determine the optimal configuration.

Matt Rennie: That distinction between “technically connectable” and “commercially attractive” seems to be becoming much more important.

Naveen: Absolutely. The grid engineer shouldn’t try to replace the market modeller or financial adviser, but we need to understand how our engineering conclusions affect them.

Curtailment is a good example. A project might technically be capable of connecting at a particular capacity, but if network constraints mean it cannot export that capacity during commercially important periods, the developer needs to understand that exposure.

The engineering work helps identify the physical constraints. Market modelling can then assess how frequently those conditions may occur, what other projects may be dispatching at the same time, and what that potentially means for generation, charging, discharging and revenue.

That interface between technical and commercial analysis is becoming increasingly important as more projects enter the NEM and congestion increases.

Matt Rennie: How different is the analysis for solar, wind, BESS and hybrid projects?

Naveen: The underlying power-system principles are similar, but the operating characteristics can be very different.

A wind or solar project is primarily exporting generation, with output driven by the available resource. A battery can move rapidly between importing and exporting, so you need to assess both charging and discharging conditions.

A hybrid project adds another level of complexity because you may have wind or solar and BESS sharing the same connection point. These projects can have different configurations, including AC-coupled arrangements, while solar and BESS can also be configured using DC coupling. The combined installed capacity behind that connection point can be significantly greater than the agreed maximum export capacity. That raises questions around how the different technologies are coordinated, how power flows through the shared connection point, plant control and operating modes, and how the project behaves under different combinations of generation and charging.

At feasibility stage, we’re not necessarily running an hourly quasi-dynamic simulation against a full year of wind, solar and battery dispatch. That type of analysis can be undertaken alongside detailed market modelling.

Our job is to identify the important power-system conditions and test the network and plant against them. Ultimately, the technical analysis and market analysis need to come together.

Matt Rennie: How early does a developer need to choose an OEM?

Naveen: I generally wouldn’t want OEM selection to prevent the developer from starting the early grid work.

At feasibility stage, location, project capacity and connection point can be more important than deciding the exact equipment.

Later, OEM selection becomes very important because the technical characteristics of the plant — and particularly the quality and maturity of its models — become critical to the connection process.

I wouldn’t automatically consider an OEM unsuitable simply because it is relatively new to Australia. Some manufacturers have extensive experience in other regions and power systems.

You need to assess the actual capability: model maturity, control modes and performance, capabilities such as thermal performance, overloading and derating, how robust and interoperable the equipment is with other OEM equipment and plant controllers, experience under weak-grid conditions, technical documentation and, importantly, the engineering support the OEM will provide while issues are being resolved through the connection process.

The brand name is less important than understanding how that equipment is actually going to behave in the power system.

Matt Rennie: Presumably this becomes even more important as we see larger batteries and more grid-forming technology?

Naveen: Yes. Grid-forming technology is a very interesting development because we’re asking inverter-based resources to provide capabilities that are different from conventional grid-following behaviour.

But “grid forming” shouldn’t simply be treated as a label.

We need to understand the control implementation, how the inverter responds to disturbances, how it performs as system conditions become weaker, how multiple units interact and whether the simulation model accurately represents the behaviour of the real equipment.

As projects become larger, those questions become increasingly material.

If you have several hundred megawatts of BESS connected at one point of connection, its interaction with the surrounding network matters. And if you have multiple projects using similar or different control philosophies within the same electrical area, you also need to understand those interactions.

That is why detailed modelling, strong OEM engagement and experienced power-system engineering remain so important.

Matt Rennie: What’s the biggest mistake you see developers make during the connection process?

Naveen: Rushing.

I understand why it happens. Every project has a programme. There are financing milestones, procurement decisions, board approvals and development deadlines. Eventually somebody asks the grid team, “Can we submit next week?”

But submission isn’t the same as progress.

If the technical package isn’t mature, the result can be a long issue tracker, repeated questions from the NSP or AEMO, model revisions and multiple resubmissions.

You might save four weeks before submission and then lose several months afterwards.

I would rather submit a technically robust package where we understand the models, assumptions and results and can confidently explain why the plant is behaving as it is.

Sometimes taking another month before submission is actually the fastest connection strategy.

Matt Rennie: What’s the equivalent mistake grid engineers make?

Naveen: Not controlling and understanding the inputs properly.

Grid studies can be very sensitive to assumptions and inputs. Equipment parameters change. OEM models change. Network information changes. The project configuration itself changes.

If different engineers are unknowingly working with different versions of those inputs, you can produce results that individually appear reasonable but don’t actually represent the same project.

That’s why good grid engineering isn’t simply about knowing how to run RMS or EMT tools.

The engineer needs to understand the power system, know what question the study is trying to answer, control the technical inputs and be able to interpret why the model is behaving in a particular way.

Software will produce a result. The engineer has to determine whether that result makes physical sense.

That distinction is extremely important.

Matt Rennie: Is that also why you see grid connection as a partnership between the developer and its grid consultant?

Naveen: Yes. I think it has to be.

Every engineer working on the project needs to take responsibility for their technical work, but somebody also needs to feel accountable for the overall project outcome.

Grid connection involves the developer, OEM, NSP, AEMO and often a number of other technical and commercial advisers. Changes made by one party can affect everybody else.

So it can’t simply be: we completed our study, here is our report.

The grid engineer needs to understand what the developer is trying to achieve and help them navigate the technical decisions required to get there.

That relationship becomes particularly important when problems arise — because on complex connection projects, there are often technical issues that need to be worked through.

Matt Rennie: Rennie has Grid Connections engineers across Australia, Malaysia and India. Does an international engineering team make a practical difference?

Naveen: It does, in two ways.

The first is delivery. On a project with a pressing timeline, an Australian engineer can finish at five or six in the evening and hand work across to colleagues in Kuala Lumpur or India. They can continue the analysis and Australia can pick it up again the following morning.

Instead of the project effectively stopping overnight, another part of the team can continue moving it forward.

But I think the technical advantage is actually more important.

Engineers from different regions have experience with different grid codes, network characteristics, technologies and approaches to power-system engineering. They don’t all arrive at the same problem with exactly the same assumptions.

When you put those engineers together, somebody may have encountered a similar technical problem in another power system and approached it differently.

That diversity of engineering experience is one of the strengths of Rennie’s Grid Connections team. We’re not limited to the experience of one office or even one power system.

And when you combine that technical capability with Rennie’s Australian market and commercial expertise, you can look at the project as a whole rather than treating grid connection as an isolated engineering exercise.

Matt Rennie: Finally, everyone says grid connection in Australia is becoming harder. Is it?

Naveen: From a developer’s perspective, it can certainly feel harder because the amount of analysis and scrutiny is significant.

But you need to understand why those requirements exist.

The NEM has some unusual characteristics. It is geographically very long, there are limitations in interconnection between parts of the system, generation can be located a long distance from major loads, and parts of the network can experience relatively weak system conditions.

At the same time, the generation mix is changing rapidly. We’re connecting very large quantities of inverter-based wind, solar and battery storage while synchronous generation is progressively reducing.

Under those conditions, AEMO and the NSPs need confidence that new plant will remain stable and behave appropriately across a wide range of credible power-system conditions.

That means the models need to be accurate, the control systems need to perform appropriately, and the interactions between the project and the surrounding power system need to be understood.

So, yes, the process is demanding. But much of that technical rigour is necessary.

I don’t think the objective should be to make grid connection “easy”.

It is also important to recognise that AEMO and the NSPs are taking steps to make the connection application process more efficient, including introducing new tools and providing additional support, while maintaining the necessary technical rigour.

The objective should be to make it technically rigorous, predictable and efficient — and to identify problems early enough that the developer still has choices about how to solve them.

Rennie’s perspective

The discussion with Naveen highlights how much the role of the grid engineer is changing.

Grid connection is no longer simply a technical approval process applied to a project once the major development decisions have been made. Increasingly, good grid advice can influence where a project is built, how large it should be, how it is configured, which technology is selected, how it operates and ultimately whether the investment case works.

A technically connectable 300 MW project is not necessarily a better investment than a 200 MW project. A larger battery is not necessarily more valuable if network constraints materially limit the charging or discharging profile required to monetise it. And an apparently attractive site can look very different once congestion, curtailment, system strength and future connections are properly considered.

This is also why Rennie sees value in bringing engineering and commercial analysis together earlier in development.

Our Grid Connections engineers can establish the physical and technical boundaries of a project. Rennie’s market and commercial teams can then assess the consequences of those boundaries for dispatch, curtailment, revenues, offtake, financing and ultimately project value.

For developers, the practical message from Naveen is a simple one:

Start the grid conversation before the project is fixed.

The most expensive time to discover a fundamental grid problem is after the land, project size, technology, OEM, commercial assumptions and development programme have all been locked in.

The cheapest time to solve it is while you still have choices.