HMI upgrade to auto start dramatically improves reliability

2015 CCJ Best Practices Awards: Best of the Best

Waterside Power, an emergency oil-fired peaking plant located in Stamford, Conn, is equipped with three trailer-mounted TM2500s. ISO New England (ISO-NE) requires this facility to meet the grid’s generation requirement within 30 minutes of an electronic or telephone dispatch. The site recently reduced staff from five employees to just three—including Plant Manager Bill Jolly.

Waterside generally took about 15 minutes to reach full load, and with manual operation required for some systems, that time increased after losing two operations positions. The only operator on shift would have to leave the control room at critical times during the startup process to energize various systems manually. Also, with fewer people on staff there was a greater chance of a missed communication and a lost generating opportunity.

Additionally, ISO-NE recently implemented much stronger penalties for not meeting the 30-min dispatch requirement and for the failure to provide reserve. This is a relatively small project and the inability to meet grid needs even one time could jeopardize the plant’s future.

To better understand the business risk associated with continuing to operate the plant in the usual manner with the reduced staff, think of one person performing the following functions using the existing startup process: Operator receives a dispatch, confirms the dispatch, and manually starts each unit while tending to auxiliary systems—some with automatic functions, some manual operation only. This might not sound so challenging until you look at the details for some of the steps involved. Consider the following:

Operator confirms the dispatch and then walks down to the fuel building to energize the fuel pumps. That task complete, the operator returns to the control room to verify all permissives have been satisfied. Now he can start the first of the three gas turbines, then the second, and finally the third (assuming all units are required).

Bear in mind that when the operator is ramping up one unit, another GT (or both units) is in a different stage of the startup process, requiring him to switch screens and tend to other needs based on a given unit’s stage of operation at that time. There’s more: While all this is in progress, the NOx system had to be started manually and the water-to-fuel ratio maintained manually to stay within air-permit limits.

Needless to say, the foregoing regulatory requirements and equipment limitations created a high-stress environment for operations personnel.

Solution. The HMI was upgraded to automatically start the plant, reduce start time, and keep the operator focused on safe operation while meeting required real-time dispatch requirements. Photos show HMI screens before and after the upgrade effort.

Full automatic-start capability is one feature of the upgraded HMI. It works this way: When a dispatch directive is received electronically, the HMI can initiate the start sequence to meet the specified output requirement anywhere in the range from 0 MW to the desired dispatch point (DDP). One of the two 100% fuel pumps is started and shutdowns are cleared. Start permissive received, the HMI brings the lead unit online. This process is repetitive for all engines and happens simultaneously.

The full-auto start option, although not preferred over the alternatives, is used mainly when the operator on shift is not at his post or is making rounds when the dispatch request is received. In this mode, when dispatched, the plant will start to come online. The operator may hear the plant starting up or he may receive a verbal dispatch order along with the electronic dispatch. In any event, he has sufficient time to return to the control room, verify a dispatch has been given, and based on that information, continue with the startup process—or not, if the dispatch order cannot be verified.

Auto start with manual initiation. Alternatively, the DDP, equipment-manufacturer operating limits, and regulatory commitments are input manually before putting the system in auto mode. These manual inputs are as follows:

      • Select a lead unit. This unit will cycle load to maintain various load changes that are received during a plant dispatch.

      • Select lag units. These units will ramp to a specified “max MW” set point. This number is based on machine operating parameters and contractual commitments with the dispatch authority; the operator can change status based on de-rates or site-specific needs at that time.

      • Select a minimum and a maximum DDP set point that complies with contractual commitments and machine capabilities. The purpose here is to not allow a false start to an erroneous DDP, or run the machines outside their design capabilities.

      • Select NOx water-to-fuel ratio to meet permit requirements; also, set the NOx-water pump to start at a desired output. This is 5 MW based on the current SOP (Standard Operating Procedure), but the plant did want the capability to adjust that because operating conditions can change.

      • Select actual generation bias. The intent here is to ensure the plant is meeting its dispatch requirement. To illustrate, assume the DDP specified by ISO NE is 46 MW. If the plant is producing less power at the 30-min mark on a reserve dispatch, the site’s performance factor would be reduced. The operators generally use a 500-kW bias; that is, no matter what the DDP, the plant tries to produce 500 kW more than the dispatch request.

Auto-start operation is initiated manually after the CRO receives and confirms a dispatch. Operators typically favor this option because it gives them the ability to verbally confirm a dispatch prior to toggling the manual/auto switch to auto. All presets and start functions are the same as for fully automatic operation, except that plant’s auto start is based on a DDP change.

Waterside BOB Figs 1, 2

Manual operation is virtually the same as the original HMI starting process, but once the plant is stable, the CRO can switch to auto to follow DDP changes automatically.

Finally, the central (control room) auto-start functions are duplicated locally in each unit’s control cab. This way, if the operator has to go to any unit for monitoring and/or troubleshooting, he can monitor, start, stop, and/or adjust any of the GTs from any unit’s local control room.

Results. Since completion of the HMI upgrade project, Waterside has responded to 29 fast-start emergency dispatches without a failure and made 40 successful starts without an operator error or a trip of any kind. Based on the plant’s historical data, these are records. The operators are less stressed today and have confidence in the system. They have more freedom to walk systems down during a dispatch, even with the staff reduction. The plant has reduced to 10 minutes the total time from dispatch to DDP. In sum, the HMI upgrade has contributed significantly to Waterside’s success and reduced the chances of missing a dispatch.

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