Supply security

To facilitate earlier failure detection, we deploy inspections in combination with data. If failures nonetheless occur, we remedy them as quickly as possible while minimising the inconvenience for our customers. On average, customers were not supplied with electricity for 19 minutes in 2021 (2020: 26 minutes). The target for 2021 was less than 17 minutes, which means that the target for average downtime was not achieved. This was mainly attributable to a failure with a major impact in the municipality of Stichtse Vecht. There were also two comparatively large failures in Rotterdam and The Hague. These three failures combined represent downtime of a little over two minutes. That is 12% of the downtime in 2021. The average downtime for gas was 29 seconds. This is well below the target of one minute for 2021.

Annual average downtime for electricity (in minutes)

Causes of downtime for electricity (in per cent)

This year, we improved our registration of the causes of failures. As a result, the percentage in the category ‘other’ decreased compared with last year (2020: 24%). The increase in the number of excavation activities in particular caused the percentage of failures due to such activities to almost double compared with last year (2020: 16%).

Annual average downtime for gas (in seconds)

Causes of downtime for gas (in per cent)

For gas, the number of causes of downtime remained relatively stable compared with last year. An improvement was visible in the category 'other'. The number of instances of excavation damage edged up (2020: 13.5%). The percentage is lower than for electricity, as the gas grid is 40 cm deeper down than the electricity grid. Fewer excavation activities take place at that depth.

Supply reliability (in per cent)

Supply reliability increased compared with the previous year. We are proud that our grids are among the best in the world.

Failures – their causes and what we do to prevent them

Ageing grids

The average age of the Stedin grid is increasing, and that is and remains a key focus area. We seek to use the materials in our electricity and gas grids for as long as possible and only replace what is absolutely necessary, in order to keep the societal costs for the energy supply at a minimum. It goes without saying that we closely monitor safety and reliability at all times. Our use of data and predictions of failure curves enable us to make progressively better choices and take timely measures. We call this 'risk-based replacement'. Targeted interventions will be needed in the years ahead to maintain the quality and safety of our grid in the long term as well. This means we must invest not only in the energy transition, but also in the quality of our grids with a view to the long term.

Failure localisation

Low-voltage failures in Rotterdam and The Hague last longer than average in our service area. We therefore conducted a pilot study in which smart meters in Rotterdam and The Hague are 'pinged’ during a low-voltage failure. The meter then indicates whether it can be reached, and this tells us whether this connection is experiencing a failure. In order to remedy a failure, it is important for the grid manager to determine in advance the extent of the failure and the grid segment in which it is situated. With that information, we can send the right number of fitters with the right skills and instruction to the failure. Failures are resolved faster as a result.

Excavation activities

In 2021, the number of activities carried out below ground increased by 10%. As a result, the number of instances of damage to our grids is also rising. The direct repair costs for this in Stedin's area of operation are around € 4 to 5 million a year. These costs can to a large extent be recovered from the party causing the excavation damage.

It is good to place the growing number of instances of excavation damage in the right context. The energy transition, construction of housing and of roads and the rapid roll-out of fibre-optic networks entail increasingly frequent excavation activities. The likelihood of damage grows in step with this, as there is hardly any room below ground in our densely built-up regions. Fortunately, we are able to limit the increase in the number of instances of damage: The 10% increase in the number of excavation activities resulted in 5% more excavation damage for Stedin. This shows that the measures we are taking to reduce the risk of excavation damage are successful.

Those measures include the following:

• We enter into covenants with telecommunications companies and municipalities on laying fibre-optic networks. This is accompanied by closer supervision by Stedin in the form of working visits and instructions for employees carrying out the work. As a result, it has proved possible to reduce the relative proportion of instances of damage caused by laying fibre-optic networks by one quarter, to around 20% of the number of instances of excavation damage.
• The 'Dig safe' campaign was continued in 2021. The campaign again had a positive effect, with the number of recorded instances of excavation damage by consumers decreasing by more than 10% in the spring.
• In the Cables and Pipelines Consultation (Kabel- en Leidingoverleg), we work jointly with all organisations that work below ground to create a joint framework for reducing the number of instances of excavation damage. Stedin has been working for a number of years in accordance with the guideline that was drawn up to prevent excavation damage (CROW 50).

Power outage with significant impact in 2021

A power outage can have a significant impact for a variety of reasons. This may be because it involves a large number of customers or a customer with critical processes that cannot be interrupted. We had one power outage with a significant impact in 2021. On Tuesday, 12 October, there was a complex medium-voltage failure in the municipality of Stichtse Vecht. As a result, 5,420 customers were left without power.

The failure lasted for more than 13 hours. It was caused by a defective cable. Owing to a telephony/data failure at the provider, that signal did not come through properly, making it difficult for us to read out information and to locate where the power outage had occurred. The power outage led to irritation and inconvenience in various places, for instance at the Merenhoef residential care home in Maarssen. Extra staff had been deployed there to be able to ensure proper care for all residents. The customers affected who were without power for more than four hours are entitled to compensation from us for the outage.

Maintenance and replacement

Smart, risk-based maintenance

Data-driven, risk-based maintenance has been accelerated. This involves us using data to pinpoint where maintenance is really needed, where it is not essential and which assets need replacing. In addition to quality improvements, this yields annual savings. The following are a few examples of how we use data for maintenance:

• Currently, we use analogue manometers to monitor below-ground oil-filled pressure cables for oil leakages. This covers around 80 connections, of 800 km in total. These meters cannot detect latent leakages in time. With the advent of digital pressure sensors with wireless communication options, it has become possible to continually monitor oil pressure and detect latent leakages in time. This can help to prevent environmental pollution.
• Stedin is also working on options for digitalisation in the gas grid to facilitate smarter working methods. A pilot project is ongoing in the gas stations to collect the information from valve positions and inlet and outlet pressure. Besides the possibility of determining energy supply, it also indicates where the protective devices may be failing. That makes it possible to send out our fitters in a targeted way and to increase effectiveness.
• Power transformers regulate the tap setting to a different voltage level or the quality of electricity supply. The number of switches of the tap setting determines the maintenance cycle of the transformer. These transformers are equipped with an analogue meter for registering the number of switches. A simple IT solution allows us to determine the registration of these switching actions more accurately, and remotely. This not only saves capacity in collecting the data but also contributes to a more effective maintenance cycle and longer useful life.

Substantial investments are also necessary to maintain our assets at the appropriate level. You can read more about this in the 'Financial, economic performance' section.

Accelerated replacement of brittle pipelines

We are required to replace brittle gas pipelines (grey cast iron and asbestos cement) before 2030. Stedin has brought this deadline forward to 2028. A total of 180 km of brittle pipelines were due to be replaced in 2021. This target has been achieved by replacing 188 km of brittle pipelines. Around 60% of the brittle pipelines have now been replaced, with 1,222 km of such pipelines remaining in our coverage area. In the province of Zeeland, 5 km of brittle pipelines were replaced in 2021, bringing the total to 90% of the number of kilometres of brittle pipelines.