Integrating Electrical Outputs with I2Sim

In this section, the structure of the electrical power system infrastructure is presented along with its integration methodology with the infrastructure interdependency software I2Sim. As the overall study was based on the effect of infrastructure interdependency during disaster, only electrical power systems will be discussed which lies within the scope of this thesis work. To understand the overall structure of the power system and its integration with I2Sim, it is better to refer to Figure 5.3, which is a reduced block diagram of the Western test case model. Figure 5.3 shows all of the major subsystems used in the Western test case during disaster events. It also presents information about the inputs and outputs of different subsystems.

In the disaster scenarios, different entities were modelled using the I2Sim software. The study case and the objectives of the disaster scenario are explained in section 2.8. To integrate all of the available entities into I2Sim, different domain simulators were chosen. The description of all chosen domain simulators is explained in Section 2.6. The campus was divided into three parts; A1: central campus, A2: UCC and social science, and A3: south campus, which are denoted by three different blocks in Figure 5.3. Different inputs are provided to the buildings in the form of different entities such as water and power.

Figure 5.3: Reduced block diagram of Western test case model

The output from the buildings is in the form of condensate return, which again goes to the feed water control and increases the amount of water available for usage. In terms of electrical power, the power house and different channels, or distribution lines, were built using I2Sim.

Figure 5.4 presents the block diagram of power distribution methodology used in the I2Sim model. All of the different blocks represented in Figure 5.4 are explained below, in detail, to provide the complete picture of the electrical power system architecture used in the final I2Sim model.

 The Power House: The power house block represents the cell in the I2Sim model which consists of substations and back-up generators. The input to the power house is the city’s electricity supply from London Hydro, which is at 27.6 kV. This block represents three different substations that supply power to the physical plant and to the entire Western campus. Physically, the output of the block is fed to all the buildings on campus, including the steam and water stations. Back-up generators are also included in the power

house cell model. The responsibility of the back-up generators is to provide power to the water station, steam station, and to some of the critical buildings on campus, in the absence of power input from the utility due to any faults, or during a disaster event. As the back-up generators are diesel generators, it is necessary to maintain a fixed amount of oil in reserve to be used in case of emergency.

Figure 5.4: Block diagram of power distribution methodology in I2Sim

 PSS Sincal: ThePSS Sincal block in Figure 5.4 represents the load flow software used to calculate the power flow values at different points in the electrical power network. The PSS Sincal block has been discussed in detail in Section 5.2.2. The input from the power house is fed into the PSS Sincal, and according to the availability of power from the power house, load flow calculations are performed and different points in the network are checked for power flow values for voltage, active, and reactive power availability. In PSS Sincal, different load flow values can be calculated for different events or scenarios and can be used to get valuable information about power availability at different points on the Western campus. The data used for modelling the network using PSS Sincal was the same as used in EMTDC/PSCAD.

 Quality of Service (QoS): QoS evaluator is the block that is connected to the output of the PSS Sincal block. The Quality of Service indicator, or evaluator, is used as a tool to indicate how the network is behaving in the event of an emergency. The value of the QoS evaluator is highest when the network is healthy. But when an emergency event is experienced, the lines in the electrical network have to be reduced or disconnected. The information from PSS Sincal is passed to the QoS, which calculates using the number of normal lines, overloaded lines, and critical lines (which always need electrical power). Accordingly, the decision maker disconnects the overloaded lines to obtain a new value of QoS, as well as a value of power actually available to be fed to the distributor block. For every load flow value change, a new value of QoS is generated, which gives the actual available power. Reduction of lines leads to the lowering of the value of QoS, which gives exact information about the healthiness of the network.

 Power Distributor Control: This block has two inputs and one output which is fed into the power distributor. The inputs are received from the power house and QoS evaluator. The power house provides the information of the amount of power that is available from three substations on campus. The QoS gives an idea about available power after load flow calculations. In power distributor control, both inputs are compared and a final signal is sent to the power distributor with information about actual power distribution. During emergency situations, the final signal sent is based on the following criteria:

i. The critical infrastructures get the required power on priority basis.

ii. The power distribution for non-critical infrastructures can be compromised.

 Power Distributor: A distributor is a block in the I2Sim model that is used to distribute entities (tokens) such as power, steam, and water through channels to various cells. In Figure 5.4, the distributor is used to distribute power, thus, it is named the power distributor. The power distributor is used to distribute available power to different buildings on campus. As the entire campus is divided into different cells, power is distributed to the physical plant and to the different buildings combined together, as different cells.

In the I2Sim model, the power distribution in the distributor can be done through three different mechanisms: Manual mode, Human Readable Table (HRT), or external mode.

i. Manual mode: In this mode, the decision maker defines a single set of output ratios. These apply until changed by the decision maker.

ii. HRT mode: In this mode, the output ratios of the distributor block are read from the Human Readable Table (HRT). Each Physical Mode (PM) contains a set of output ratios. By changing the PM, the user can change the output ratios available to the distributor.

iii. External mode: In this mode, a number of input ports appear on the block. The decision maker can define the number of output ports using the number of outputs edit box. The number of the distribution factor port will be one less than the number of outputs, as the last factor is calculated internally.

All three above stated distribution methods can be used. In this study for power distribution, the manual mode was used. Special care is taken to ensure that the Physical Plant always receives electrical power to generate the required amount of steam needed to sustain the campus activities. Thus in this work, the Physical Plant is considered to be a life critical system.

 Physical Plant: The Physical Plant is the most important building to the Western community, as it has boilers installed for producing steam for the campus and University Hospital. During the winter, heating is the main priority for running any kind of business or educational institution. During the winter season at Western, the Physical Plant produces the required steam. The Physical Plant uses a combination of five of the installed boilers to produce steam. As such, during a disaster situation, it is necessary to keep the Physical Plant working to provide the necessary heating for the campus. The output of the Physical Plant is steam, for which it requires different types of inputs. In this thesis, the focus is on only one of the inputs to the Physical Plant: the electrical power input. In the I2Sim model, various distribution strategies were employed for electrical power to receive the best decision making scenarios in case of a disaster event. These are presented in Section 5.4.