Scada chosen for railway upgrade

Catapult iPower Scada has been selected to operate the electrification system of 400km of the North Island Main Trunk in New Zealand.

New Zealand Railways has selected Catapult Software's iPower Scada to replace the system used to operate the electrification system for part of the New Zealand rail network.

The North Island Main Trunk (NIMT) is one of the most important railway lines in New Zealand.

Catapult iPower Scada has been selected to operate the electrification system of 400km of the NIMT that has been electrified since 1988.

Locomotives draw power from a single-phase catenary cable suspended above the centre line of the tracks, operating at 25kV 50Hz AC.

Electricity is supplied into the system from New Zealand's national electricity transmission network through four major substations.

There are also another 12 switching points spread along the tracks length.

The main goals of the Catapult iPower Scada implementation project were to use industry-standard hardware and software, minimising the exposure to proprietary equipment, plus ensuring ongoing and economical upgrades; implement a reliable, fault-tolerant and easily supported Scada; and achieve a modern, easily configurable user interface.

The system also had to retain the existing RTUs; provide open access to Scada historical and real-time information via modern database interrogation facilities such as SQL; have an expandable client/server architecture, allowing for future growth; and enable support for modern protocols such as DNP3 to support RTUs from multiple vendors.

"Our existing Scada was obsolete".

"We risked total loss of Scada because hardware spares were quickly becoming unavailable".

"The Catapult iPower system is reliable, and sustainable in the long-term", Stefan van Greunen, Project Engineer, Ontrack.

"This was Catapult's first railway electrification Scada project".

"Many of the requirements, such as substation switching operations, were similar to those of our electric utility customers".

"However there are operational differences that we have learned about during this project".

"Ontrack has been generous in including us in the development process, and we will continue to work with them to deliver the perfect system for their operators", says David Ganley, Engineering Manager, Catapult Software.

Providing system operators with a clear overview of the status of a 400km long system was a critical objective.

The Catapult iPower Scada system summarises the status across two adjacent monitors.

Each LCD panel is 1920 pixels wide by 1200 high.

Several tools in the iPower Scada HMI were used to complete the look and feel.

On-screen buttons below each substation provide access to detailed substation one-line diagrams.

The iPower menu along the top is configured to provide alternative single-click access to detailed substation one-line diagrams for any of the 16 substations.

iPower menu "back" and "forward" buttons provide simple navigation between commonly used pictures.

The iPower menu provides "favorites" so that each operator can easily get to their own commonly used pictures.

The iPower alarm grouping facility was used to flash the substation name if there are any alarms at that substation.

An alarm also triggers a local alarm horn and sends pager messages to operators.

"Our operators may only work in the control room one week in every four, so it is important that Catapult iPower is intuitive and easy to learn".

"Our Scada training program has become much simpler as a direct consequence of installing Catapult iPower".

"However we introduced Catapult iPower to users with years of experience operating entirely from a hard-wired mimic panel".

"The very nature of the electrified train line lends itself to a wide mimic".

"Compressing this onto dual-screen workstations has been a difficult process, but switching operations in substations are much easier with Catapult iPower".

"Nevertheless we are still considering enlarging the operational workspace", says John Skilton, Manager Innovative Technology.

Standard Catapult iPower functionality is used to determine live line status.

Circuit breakers or isolation switches at the end of each line segment are tested to determine if the segment is live.

A section is considered live if all segments within it are live and the section end isolators are closed.

Live line status is shown by colouring the line using the standard Catapult iPower animation capability.

The complete live line display was implemented without any customer code or scripts, making it easy to understand and maintain.

Adjacent sections of the catenary wire that supplies trains with electricity are normally fed from different phases.

Interlocking of circuit breaker controls within Scada is critical to prevent out of phase sections being connected.

Logic is implemented using standard Catapult iPower tools to interrogate the status of the appropriate isolation devices.

It is common to have a CB control dependent on the status of 10 telemetered inputs.

Interlocking logic is escalated upwards in successive equations representing progressively larger segments.

This structure reflects the design of the network and facilitates ordered implementation of interlocking equations.

Interlocking is also designed to be fail safe.

A control is blocked if the state of any pre-check point is not definitively known because of bad or invalid data caused by, for example, loss of communications.

Operator-initiated controls and unauthorised operations are counted separately for key circuit breakers.

These analogue values are stored historically, providing information used to schedule preventative maintenance work.

"The hardware device used to convert Conitel communications to the DNP protocol had a weakness that was only uncovered during installation".

"Though the problem was not with Catapult Software, they were diligent at working through the problem, including setting up an in-house test system".

"It took some time to resolve, but since then communications has worked well and the system has been very reliable", says John Skilton, Manager Innovative Technology.

"Catapult iPower is a far more open system".

"The potential to interface with our other IT systems is something we have not yet taken advantage of, but it was an important part of making a good long-term IT investment", says John Skilton, Manager Innovative Technology.

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