University Gets Smart With Emergency Power Systems
With thousands of students living on campus, and working in classrooms and labs, plus the 24/7 need for data centers and security systems, Michigan Tech University could not operate during power outages without a backup emergency power system.
Michigan Technology University (MTU), in Houghton, Mich., needed reliable standby emergency because of power outages during extreme winter weather conditions, including very high winds. With thousands of students living on campus, and working in classrooms and labs, plus the 24/7 need for data centers and security systems, MTU could not operate during power outages without a backup emergency power system.
To meet this need for Michigan Tech, Enercon Engineering designed and built custom engineered controls and switchgear to operate an emergency backup power system using four Caterpillar 3516 diesel engine powered generators provided by FABCO Power Systems (rated total: 9 MW, 12,470 V).
Using its touch-screen control system, Enercon Engineering engineered and manufactured the medium-voltage switchboard lineup, consisting of four generator control cubicles, one incoming/master cubicle, and one remote panel to interface with existing gear. The switchgear meets applicable NEMA and ANSI standards. The gensets are automatically paralleled with the utility using Enercon controls and switchgear, and the system can be remotely monitored using an Enercon custom programmed SCADA system.
The following modes can be initiated locally at each generator, at the master, or remotely:
1. Sequence of operation: Automatic operation
The following modes are initiated from the controller.
- Individual base load: The individual genset starts in this mode.
- System-base load: The master system controller sends a start signals to the generators under its control.
- In both individual base load and system-base load modes, the loads are paralleling with the utility, soft load to the generator controller base load setpoint, and remain paralleled to the utility.
- Import/export mode: In this mode, the master system controller sends a start signal to the generators under its control. They will start and parallel to the utility. The system controller monitors the utility input and adjusts the gensets’ output to maintain the utility import or export power level setpoint up to the capacity of the system.
2. Closed transition to emergency mode-zero power transfer (ZPT)
In this mode, the utility is still available but the system requires operation in an islanded mode. Upon the operator entering this mode, the gensets shall start. The generator tie is closed and the generators are paralleled to the bus. The generators are all soft-loaded until the power flow across the utility tie breaker is near zero. The controller then opens the utility breaker, and the engines continue to carry the university load for the duration.
Note the following about the ZPT and semi-automatic modes:
- Power factor is controlled by the system or generator controller as appropriate to a preset value that can be modified.
- In the event that the utility breaker opens while the generators are operating in these modes, the generators shall automatically go into isochronous load-share mode and continue to carry the university load.
- Provisions were made under each mode for the operator to change the system-base-load setpoint, which allows the engines to soft load or unload to the system setpoint based on their rated capacity. When this mode is exited, the gensets soft unload, disconnect from the utility at an unload trip point of approximately 100 kW, and go into cool-down mode for a predetermined time, after which the engine shuts down. Each unit is capable of being unloaded individually without affecting the operation of the other units.
3. Loss of primary utility feed
Should the primary utility feed fail, the system shall automatically revert to the secondary utility feed, provided it is available. Once transferred, the current utility feed shall become the primary feed until it fails or the operator changes it. Simply changing the primary utility feed (while the generators are off-line) will result in an open transition. In order to complete a closed transition change of the primary utility feed, the operator will first enter the ZPT mode as described above, and then change the primary utility feed. Upon exiting the ZPT mode, the system will synchronize to the selected primary utility feed, completing the closed transition change.
4. Emergency (generator) auto-standby mode
In the event there is a failure of the utility supply, the controller trips the utility main breaker and the university feeders. The controller starts up the gensets. The first generator up to voltage and frequency is closed to the dead bus. The remaining generators automatically synchronize and parallel to the bus as they come up to voltage and frequency. At this point, the controller closes the university feeders one by one. When the utility supply has returned, within proper limits, the control system brings the generators into synch with the utility, and closes the utility breaker. The gensets shall then soft unload. A load shed/add feature is incorporated in the controller in the event the university load exceeds the generators on line capacity.
5. Remote operation mode: Remote base load
In this mode, the gensets operate in system-base-load mode. Upon receiving a start signal from the remote dispatch, the generators start and parallel automatically to the utility starting. Provision was made to block remote starting during periods of maintenance.
6. Manual operation
- Manual mode: This mode is intended to be a backup mode in the event of a processor failure or generator control module (GCM). It is also used for black start operation in the event the utility is lost and loss of communication between the switchgear and the remote panel has occurred. In an islanded mode, once the utility is opened, the unit automatically switches to isochronous load-share mode. For this mode, a separate kilowatt and power factor meter is provided to monitor the load.
- Base load: In this mode, each genset manually starts and comes up to rated speed and voltage. The operator turning on the synch switch and manually adjusting the voltage and speed to bring the generator into synch with the utility, using the synchronizing panel, manually synchronizes the genset. The operator then closes the generator breaker and loads the engine to the required base load setpoint, using an isochronous manual load control system. Closure of the generator breaker is supervised by the generator protective relay synch check contact. Provision is made for power factor control in this mode. To exit this mode, the operator reduces the load on the generator until about 100 kW, at which point the operator trips the generator breaker. The engine should then be set to cool-down mode where the engine will shut down after the required cool-down time. In the event the utility breaker trips while in the above mode, the generator will automatically be connected in isochronous load-share mode and continue to carry the university load as appropriate.
- Black start: In the event there is a failure of the utility supply and loss of communication, the operator trips the utility main breaker and the university feeders. Then each generator is manually started. Closure of the first generator breaker is supervised by dead bus closing in the generator protective relay. Remaining generators are then manually synchronized by the operator turning on the sync switch and adjusting the voltage and speed utilizing the synchronizing panel. At this point the university feeders are closed, as determined appropriate by the operator.
The SCADA system is made up of a general control module, an intelligent gateway (UIG) with data link interconnections, and an operator interface module (OIM) for display read-outs and selected control functions. The OIM is 12-in. high-resolution color touch-screen with metering displays, selected control functions, and annunciation displays. The control system includes automatic synchronization, for the site genset, with analog or pulse width modulated (PWM) outputs to the engine governor control and analog or binary outputs to the generator auto-voltage regulator, resulting in both speed (frequency) and voltage matching.
- Power metering display for the site genset with simultaneous digital read-outs of following minimum parameters:
- AC amperes in each of the three phases
- AC voltage of each phase to phase
- Kilowatts, three phase
- kVARS, three phase
- Power factor
- Kilowatt hours, three phase, accumulative
- Kilovar hours, three phase, accumulative.
- This metering display is provided as a single screen on Enercon’s operator interface module, allowing all parameters to be viewed simultaneously.
- For manual paralleling (in addition to auto-paralleling) of the genset to the bus, the following digital parameters are simultaneously displayed:
- AC voltage, incoming genset
- AC voltage, bus
- Frequency, incoming genset
- Frequency, bus
- Synchroscope (via touch screen).
- A synchronizing switch was provided, for the genset, along with manual adjustments of genset voltage and frequency via raise/ lower push-button functions.
- Power and control functions to include the following for the genset:
- True RMS real power sensor for precise control
- Closed loop control of genset power levels
- Control outputs (analog or pulse width) to engine governor module
- Control outputs (analog or binary) to generator automatic voltage regulator.
- Adjustable ramp time for genset soft loading/unloading
- Automatic genset loading control
- Automatic synchronization, speed (frequency), and voltage matching
- Generator available sensing to determine when operating voltage and frequency are established
- Synchronizing check function
- Genset control selector functions for automatic, manual, stop-cool-down modes of operation and off-reset for shutdown faults plus interface logic with engine auto start/stop cranking controls.
- SCADA Software Package is comprised of the following minimum configured screens:
- System one line diagram: This diagram displays power operational data of individual gensets (amperes, power factor, kW, kVARS, kWHRS), whether the gensets are on- or off-line. If off-line, the diagram will determine for what reason, system (bus) electrical data (voltage, frequency) plus utility source operational data based on a multiple genset plant, should genset source and utility source be paralleled including amperes, voltage, frequency, power factor, kW, kVARS, kWHRS, and whether imported from the utility source or exported into the utility grid.
- Generator electrical metering: Individual screens for each genset to include amperes in each of the three phases, voltage of each phase to phase, frequency, power factor, three-phase kW, three-phase kVARS, three-phase kilowatt hours along with genset online hours.
- Generator annunciations: Individual screens for each genset to include electrical monitored faults whether programmed for alarm or shutdown (under/over voltage, over/under frequency, reverse power, reverse reactive power, current unbalance, phase sequence voltage problem, breaker over current trip) plus emergency stop push-button activation, summary engine alarm and summary engine shutdown fault, low engine battery voltage, five (5) additional remote discrete fault inputs programmable for alarm or shutdown, and date/time coding.
- System annunciation: Common screen with five remote discrete inputs programmable or alarm or shutdown and should genset plant operate in parallel with a utility source, utility monitored electrical faults to also be displayed (under/over voltage, over/under frequency, rapid change in frequency, excessive voltage vector change, utility source breaker over current trip) and date/time coded.
- Utility source electrical metering: Common screen, if utility source paralleled with the genset plant, with display read-outs similar to generator electrical metering screens
- Historical trend charts: To involve any data logged within the software package with the parameters (read-out displays) and time base to be selectable by the plant SCADA operator—SCADA operator to configure designated trend data by selecting logged data points.
- PC to be part of the SCADA system equipment with software programs installed and verified. PC equipment to include color monitor, mini tower case, modem, printer port, serial communication ports, keyboard, mouse, necessary drives, network interface card, ink jet color printer, and UPS with surge suppressor.
- Protective relays
- To provide the optimum protection for their investment in the power system, protective relays were set and tested at site. Most settings are dependent upon many system variables including short circuit currents, grounding systems, and utility standards, to name a few.
- This project included supplying the protective relaying devices listed in the system description. While Enercon Engineering provided these devices, the responsibility for calculating the settings, setting the devices, and performing final acceptance testing rested with MTU.
- Multifunction relays were included with software for control logic and/or communication functions that were installed at the factory and recorded as part of the product documentation.
Michigan Tech University has established an agreement to sell back unneeded power from its facility and reduce its energy bill demand costs by reaching an emergency standby agreement with the local utility company.
Information provided by Enercon Engineering.
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