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Protection Of Industrial Power Supply Systems (Fuses, MCCBs and Overcurrent Relays Settings)
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Calculate Required Air ventilation and Heat generation of D.G Set
Heat Generated by Generator:
- For generator set installations, the heat radiated by the generator can be estimated by
- H (kW) =P X ((1/Eff)-1)
- H (Btu/min) =P X ((1/EFF)-1) x56.9
- Where:
- H = Heat Radiated by the Generator (kW), (Btu/min)
- P = Generator Output at Maximum Engine Rating (kW)
- Eff = Generator Efficiency % / 100%
- Example: 975 kW standby generator set has a generator efficiency of 92%. The generator radiant heat for this genset can be calculated as follows.
- P = 975 kW
- Efficiency = 92% = 0.92
- H = 975 x ((1/92%) – 1)
- H= 84.78 kW
- H = 975 x ((1/92%) – 1) x 56.9
- H = 4824 Btu/min
Types of Ventilation System:
- Type:1 (Preferred Design) (Routing Factor of 1)
- Outside air is brought into the engine room through a system of ducts. These ducts should be routed between engines, at floor level, and discharge air near the bottom of the engine and generator. .
- Ventilation air exhaust fans should be mounted or ducted at the highest point in the engine room. They should be directly over heat sources. This system provides the best ventilation with the least amount of air required.
- Type 2 (Skid Design) (Routing Factor of 1)
- Outside air into the engine room through a system of ducts and routes it between engines.
- Type 2, however, directs airflow under the engine and generator so the air is discharged upward at the engines
- The most economical method to achieve this design is to use a service platform. The platform is built up around the engines and serves as the top of the duct
- Ventilation air exhaust fans should be mounted or ducted at the highest point in the engine room. They should be directly over heat sources.
- This system provides the best ventilation with the least amount of air required.
- Type 3 (Alternate Design) (Routing Factor of 1.5)
- If Ventilation Type 1or Type 2 is not feasible, an alternative is Type 3; however, this routing configuration will require approximately 50% more airflow than Type 1.
- Outside air is brought into the engine room utilizing fans or large intake ducts. The inlet is placed as far away as practical from heat sources and discharged into the engine room as low as possible. The air them flows across the engine room
- Ventilation air exhaust fans should be mounted or ducted at the highest point in the engine room. Preferably, they should be directly over heat sources
- Type 4 (Less Effective Design) (Routing Factor of 2.5)
- If Ventilation Type 1, Type 2 and Type 3 are not feasible, then Type-4 method can be used; however, it provides the least efficient ventilation and requires approximately two and a half times the airflow of Ventilation Type 1
- Outside air is brought into the engine room using supply fans, and discharged toward the turbocharger air inlets on the engines.
- Ventilation exhaust fans should be mounted or duct from the corners of the engine room
- This system mixes the hottest air in the engine room with the incoming cool air, raising the temperature of all air in the engine room.
- It also interferes with the natural convection flow of hot air rising to exhaust fans.
- Engine rooms can be ventilated this way, but it requires extra large capacity ventilating fans.
Ventilation for Generator:
- When Generator set installations in Room proper ventilation is required for Generator set.
- A properly designed engine room ventilation system will maintain engine room air temperatures within 8.5 to 12.5°C (15 to 22.5°F) above the ambient air temperature.
- For example, If the engine room temperature is 24°C (75°F) without the engine running, the ventilation system should maintain the room temperature between 32.5°C (90°F) and 36.5°C (97.5°F) while the engine is in operation.
- Ensures engine room temperature does not exceed 49°C (120°F).
- Required Ventilating Air is calculated as
- V=((H / D x Cp x T)+ Combustion Air) X F
- Where:
- V = Ventilating Air (m3/min), (cfm)
- H = Heat Radiation i.e. engine, generator, aux (kW),(Btu/min)
- D = Density of Air at air temperature 38°C (100°F). The density is 1.099 kg/m3 (0.071 lb/ft3)
- CP = Specific Heat of Air (0.017 kW x min/kg x °C),(0.24 Btu/LBS/°F)
- T = Permissible temperature rise in engine room (°C), (°F)
- F = Routing factor based on the ventilation type
- Example: The engine room for generator set has a Type 1 ventilation routing configuration and a dedicated duct for combustion air. It has a heat rejection value of 659 kW (37,478 Btu/min) and a permissible rise in engine room temperature of 11°C (20°F).
- V=((659 / 1.0099X0.017X11)+ 0)X1
- V = 3206.61 m3/min
- V=((659 / 0.071 X 0.024 X 20)+ 0)X1
- V = 109970.7 cfm
January 01, 2018 at 08:40PM by Department of EEE, ADBU: http://ift.tt/2AyIRVT
It’s About Time. Engineers, Happy New Year!
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What is WiMAX? Difference between Broadband WiMax and WiFi
What is WiMAX GSM Broadband and WiFi
Introduction to WiMAX Broadband
WiMAX stands for Worldwide Interoperability for Microwave Access, a standard based wireless communication technology to provide high speed, long distance broadband connectivity for domestic and business purposes. It works on the principle of Orthogonal Frequency Division Modulation technique. It is a 4th generation wireless mobile access technology.
Also Read: What is ZigBee Technology and How it works?
Operating principle of WiMAX is same as that of Wi-Fi. A computer or a laptop, which is equipped with WiMAX, would receive data from the transmitting station, using encrypted data keys.
WiMAX system consists of a WiMAX tower and a WiMAX receiver. A WiMAX tower can provide coverage to a large area, whereas a WiMAX receiver can be a laptop or a Personal Computer Memory Card International Association (PCMCIA) card.
The tower station can be connected directly to internet using high bandwidth, wired connection or to another tower station using Line of Sight, Microwave link.
WiMAX connection is accessible to residential areas through interface options like RJ-4 Ethernet connection and RJ-11 telephone connection. For business applications, interface options include T1/E1 interface with a 10/100 BT Ethernet connection.
So as per definition, WiMax seems to be like Wifi, so where lies the difference? Here in this article, Let us discuss about few points which makes WiMAX different to Wi-Fi.
Also Read: An Overview of RFID Based Library Management System
IEEE Standards of WiMAX & Wifi
While Wifi is based on IEEE 802.11 standard, WiMAX is based on IEEE 802.16 standard. IEEE 802.11 standard (Wireless Local Area Network (LAN) working group) is used to provide Wireless Local Area Network (WLAN) standards for short distance wireless networks. Popular versions are IEEE 802.11b, 802.11g and 802.11n.
IEEE 802.16 standard (Broadband Wireless Access Working Group) is like IEEE 802.11 standard in architecture, difference being in its application to provide standards for Broadband Wireless Metropolitan Area Networks (WMAN). It employs medium access control (mac) as well as physical layer specifications, allowing multiple physical layers. Popular versions are 802.16a, 802.16d and 802.16e.
Range
WiMAX provides both line of sight as well as non-line of sight connectivity. For line of sight connectivity, with the help of strong antennas, coverage area of up to 9300 square kilometers (sq-kms) is possible. Non-line of sight connectivity is like Wi-Fi connection. WiMAX covers a radius of 50 kilometers (km).
On the other hand, Wi-Fi is a short distance wireless means of connectivity up to 30 meters for indoor applications and up to 100 meters for outdoor coverage. Unlike WiMAX, Wi-Fi provides only line of sight connectivity.
Operating Frequency Band
WiMAX technology provides two types of wireless services – Line of sight service with operating frequency band up to 66 GHz, whereas for non-line of sight service, the operating frequency is between 2 to 11 GHz.
The higher frequency range was set by the original 802.16a standard, whereas the lower frequency range was set later by the 802.16d standard, allowing less attenuation and improved performance. While 2.5 to 3.5 GHz frequency band is licensed, the 5.8 GHz frequency spectrum is unlicensed.
On the contrary, Wi-Fi operates in the unlicensed 2.4 GHz and 5 GHz bands.
Channel Bandwidth
WiMAX networks have flexible channel bandwidth range from 1.25 MHz to 20 MHz, whereas Wi-Fi networks have fixed channel bandwidth of 20 MHz.
Aslo Read: What are Industrial Communication Networks? An Overview
Communication Type
WiMAX supports full duplex communication with 256 FFT OFDM (Orthogonal Frequency Division Modulation) along with single carrier and 2048 FFTOFDM technology. On the other hand, Wi-Fi supports half duplex communication with 52 FFT OFDM technology.
Operating Forums
WiMAX spectrum is owned by WiMAX Spectrum Owners Alliance (WiSOA), which is responsible for regulating, commercialize and deploy the WiMAX spectrum in 2.3 to 2.5 GHz and 3.4 to 3.5 GHz ranges. The WiMAX standard is certified by WiMAX forum, which is an industry led, non-profit organization for promoting and certifying IEEE 802.16 compliant broadband wireless products.
On the contrary, Wi-Fi is certified by Wi-Fi Alliance, a global organization which certifies interoperability of IEEE 802.11 compliant wireless products and promotes the global wireless standards.
Data Rates
Wi-Fi can transmit data at the fastest, up to 54 Megabits per second, whereas speed for WiMAX can reach up to 70 Megabits per second. It currently provides 40 Megabits per second for one wireless channel for both fixed and mobile applications.WiMAX can deliver uplink speed of 25 Megabits per second (Mbps) and downlink speed of 63 Megabits per second (Mpbs). Updated version of WiMAX is expected to deliver speed up to 1 Gigabits per Second (Gbps).
Security
WiMAX uses encryption techniques like Triple Data Encryption Algorithm and Advanced Encryption Standards, whereas Wi-Fi uses Advanced Encryption Standards and RC4.
Wi-Fi provides security methods like Wireless Protected Access (WPA), Wireless Protected Access (WPA2) and Extended Extensible Authentication Protocol (EAP). However, it does not has any Quality of Service (QoS) management yet.
WiMAX uses security protocols like Privacy Key Management Protocol Version 2 (PKMP2), Extensible Authentication Protocol (EAP) and Advanced Encryption Standard (EAS). These protocols ensure Quality of Service (QoS) protection of both audio and video streaming services.
This feature allows service providers to manage the network traffic based on the subscriber agreement and charge the subscriber extra for Quality of Service (QoS) protection.
Mobility
Wi-Fi currently provides the fixed version, the mobile version being in development. On the other hand, WiMAX provides both fixed and mobile versions. The fixed version (802.16d and 802.16e) is used for residential as well as business areas, whereas the mobile version is seen to replace existing mobile network technologies like GSM or CDMA.
Also Read: Internet of Things (IOT) and Its Applications in Electrical Power Industry
Future with WiMAX
WiMAX seems to be the promising next generation wireless network platform, with high speed and large coverage area capabilities. It does not require line of sight and can efficiently bandwidth intensive applications like real time video. In simple words, using WiMAX, one can listen to music and watch videos on his/her electronic device.
WiMAX is currently expected to replace existing DSL and other cable broadband technologies like various companies are employing WIMAX to provide broadband connections.
It can also be a replacement for mobile communication technologies like GSM and CDMA. Using WiMAX, point to point connections can be created, with a transmission rate which can support multiple E1 and T1 lines.
By ensuring Quality of Service and Multicasting services, WiMAX can provide Voice over Internet Protocol (VoIP) and Internet Protocol Television (IPTV) apart from fast broadband connections. Also, large banks can use WiMAX networks for connecting branches and Automated Teller Machines (ATMs) to the same network.
So, this is a basic overview about WiMAX. This might be a new technology for beginners to learn, but the implementation has already been started, even in African countries. While WiMAX is the latest step in the area network scale, the final step would be the Global Area Network (GAN) (Proposed Standard – IEEE 802.20). Any latest updates regarding WiMAX and GAN is welcome in the comments section below.
You may also read:
- What are Industrial Communication Networks? An Overview
- Batteries Wiring Connections and Diagrams
- Lighting Design Calculation in a Building – Step by Step
The post What is WiMAX? Difference between Broadband WiMax and WiFi appeared first on Electrical Technology.
December 15, 2017 at 08:06AM by Department of EEE, ADBU: http://ift.tt/2AyIRVT
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