Meaning and calculation method of electric load calculation for weak motor room

The equipment room is used as a place for high-density storage of equipment, and the power consumption is very large. According to statistics, 70% of the maintenance costs after the completion of a data center computer room are electricity bills, and no one else is thinking of ways to cool the computer room. There are built in the mountains, underground, and built in the sea, power saving is really not easy! Compared with power saving, the power consumption of the equipment room is also a big problem. Today, we will introduce the calculation method of the engine room load. Understanding this is the basis of safe use of electricity, this is very important content, let's take a look.

First, the purpose and significance of load calculation

The statistical calculation of the load in the design of the low-voltage power supply and distribution system is an important content. The load calculation results play a decisive role in the installation of power supply capacity, the selection of power supply and distribution equipment, and the safe and economic operation. The purpose of load calculation is to:

1. Calculate the load current and apparent power of the transformer in the substation, as the basis for selecting the capacity of the transformer.

2. Calculate the load current flowing through each major electrical equipment (circuit breaker, disconnector, bus, fuse, etc.) as the basis for selecting the equipment.

3. Calculate the load current flowing through each line (power supply line, high and low voltage distribution line, etc.) as the basis for selecting the line cable or wire cross section.

4. Calculate the peak load, which is used to protect the setting calculation of the appliance and verify the starting condition of the motor.

Second, the load calculation method

In China, the demand coefficient method and the binomial coefficient method are generally used to determine the load of electrical equipment. The coefficient method is the most commonly used method for determining the calculation load in the world. The most convenient method is to determine the number of equipment. It is reasonable to calculate the load of the branch trunks with few differences in the capacity of each equipment; in the building power distribution, the load density method and the unit index method are also commonly used to calculate the load. The unit index method can be used in the design stage of the plan; in the preliminary design and construction drawing design stage, the required coefficient method should be adopted.

Third, the principle of load calculation

When calculating the load, the equipment power should be calculated according to the following principles:

1. The rated power of the electrical equipment for different working systems shall be converted to a uniform equipment power.

2. The equipment power of the rectifier refers to the rated AC input power.

3. The equipment power of a group of powered devices shall not include spare equipment.

4. When the calculated active power of fire-fighting electricity is greater than the fire, the general power and lighting load may be cut off at the same time. The general power, lighting load plus fire load shall be used to calculate the total low-voltage equipment power and calculation load. Otherwise, the fire load should not be considered when calculating the total low pressure load. When there is a load that is used in combination with the fire load, the part of the load should also be included in the general power and lighting load.

5. The single-phase load should be equally distributed to the three-phase. When the total calculation capacity of the single-phase load is less than 15% of the total calculation capacity of the three-phase symmetric load in the calculation range, all are calculated according to the three-phase symmetric load; when it exceeds 15% The single-phase load shall be converted into an equivalent three-phase load and then added to the three-phase load.

Fourth, the data center related experience summary

The load calculation is the basic calculation of the power supply system design, and the load calculation in the data center is more suitable to use the required coefficient method. The calculation of the need for the value of the coefficient, load factoring, battery charging and air conditioning lighting estimates, etc., in the calculation of the data center is still different from other building professional calculations, is summarized as follows:

1. The IT load of the data center is of high importance. Equipment such as UPS must be used to ensure uninterrupted power supply. UPS will adopt “1+1”, “2+1” and “2N” according to the construction standards of the data center. And other different configurations. Since the power supply department needs to calculate the total installed capacity of the equipment room, the rated capacity of the IT equipment in the data center should use the total installed capacity of the UPS equipment. The required factor for calculating the capacity of the IT equipment is adjusted according to the configuration of the UPS equipment, that is, the required coefficient = the number of UPS configurations of the primary UPS equipment. For example, when the UPS performs the load calculation according to the 2N setting, the coefficient needs to be taken as 0.5.

2. The battery charging capacity of the UPS configuration shall be included in the load calculation. Depending on the construction standards of the data center, the UPS battery needs to be configured according to different backup times, that is, the battery capacity and number of groups configured for each UPS are different. UPS battery charging capacity = current × voltage × group number × efficiency According to the calculation, the UPS battery charging capacity is about 10% to 20% of the UPS configuration capacity. When doing load calculation, the conclusion can be directly applied to simplify the calculation.

3. In the data center, in addition to the IDC rack, the air conditioner accounts for a large proportion of the total load. Generally, the standby air conditioner is configured, and the standby quantity varies according to the construction level of the data center. The required factor for calculating the capacity of the air-conditioning equipment is adjusted according to the configuration of the air-conditioning equipment, that is, the coefficient = the number of main air-conditioning equipment / the number of air-conditioning configurations. In 2007, the green network organization developed the data center energy efficiency ratio indicator PUE, which is widely used in the industry. PUE=data center total energy consumption/IT equipment total energy consumption. According to the data analysis of the data center, the PUE value of the data center is generally between 1.6 and 1.8, that is, the air conditioning and lighting load of the computer room is about 60% to 80% of the load of the IT equipment, and the lighting load is compared with the air conditioner. It is quite small, so it can be approximated that the air conditioning load of the computer room is about 60%~80% of the load of the IT equipment. This conclusion can be directly applied to the load calculation to simplify the calculation.

4. According to relevant experience, the lighting load is generally estimated according to 30w/m2, the office air conditioning load is generally estimated at 50w/m2, the restaurant is powered by 2kW/person, and the gas is estimated at 5w/person.

5. According to the load calculation requirements, seasonal consumers should choose the largest one to be included in the total equipment capacity. The data center air conditioning load is generally far greater than the heating load, so you only need to calculate the air conditioning load when calculating.

6. According to the load calculation requirements, the fire equipment capacity is generally not included in the total equipment capacity, so the fire elevator is not included in the calculation.

7. According to the requirements of the power supply department, the power factor after reactive power compensation needs to reach 0.95 or above, and is generally compensated according to 30% of the transformer capacity.

8. According to relevant empirical data, the simultaneous coefficient in the load calculation is 0.9-0.95.

V. Case analysis

This article takes a new data center of an operator as an example: the construction standard is Toer IV, the IDC engine room is about 1000m2, the new IT equipment with 5kW power consumption is 50, the IT equipment with 100kW power consumption is 50, and the air conditioning and lighting in the IDC room. According to the matching configuration (the air conditioning system is not considered to be powered by the UPS system). The equipment room of transformer and power distribution and UPS is about 1000m2, and the office area is about 1000m2. The fire elevators are equipped with 1 unit and 1 unit, and the equipment capacity is 50kW/set. The office has 2 electric heating units with capacities of about 80kW and 50kW respectively. It is required to determine the equipment configuration of the data center power supply and distribution system through load calculation.

Step 1: Determine the system configuration that powers the IT equipment

According to the "Uninterruptible Power Supply for Communication - UPS" (YD T095-2008), the requirements for outputting active power of UPS equipment are: ≥ rated capacity × 0.7kW / kVA, therefore, the configured UPS capacity should be: (200 * 5 + 50 *10) / 0.7 kVA = 2142.86 kVA. The IDC equipment room is set up according to the Tier IV standard equipment room. The UPS equipment is considered according to the 2N configuration. The total capacity of the configured UPS equipment should not be less than 4285.71kVA. This project requires the construction of two sets of "3+3" parallel 400kVA UPS power systems. The battery pack of the UPS mainframe is considered to have a backup time of 15 minutes at a full load (the discharge termination voltage of a 2V battery cell is 1.8V). Each UPS device is equipped with three sets of 200AH battery packs, for a total of 36 groups.

Step 2: Perform load calculation

The elements that need to be calculated: UPS, UPS battery charging, computer room air conditioning and lighting, office area air conditioning and lighting. And according to the requirements of the power supply department, reactive power compensation.

Step 3: Calculate the results and configure the device based on the load

According to the load calculation, the total AC load is about 6425.36 kVA, and the required load of the oil machine is 6032.88 kW. According to the requirements of Tier IV and power supply configuration, it is proposed to set up two 10kV mains introductions, and the two-way mains should meet the capacity of one-way full load. Install 1 set of high-voltage switchgear (including 2 inlet isolation cabinets, 2 inlet cabinets, 2 measurement cabinets, 2 communication cabinets, and N outlet cabinets); install 4 sets of 2000kVA dry-type transformers; low-voltage drawer type switchgear 2 sets (each set includes 2 incoming line cabinets, 2 oil machine mains conversion cabinets, 1 low voltage communication cabinet, N low voltage feeder cabinets, 4 low voltage capacitor cabinets); 4 1600kW diesel generator sets are installed.

Combined with the above examples, I believe that everyone has a clearer understanding of how to load computer rooms. The computer room is a large "power". The safety of the power supply in the computer room cannot be ignored. The safety of the power supply can guarantee the stable operation of the computer room.