Telecommunications is an interesting, and vast subject in the field of Engineering. The profession, “Telecommunications Engineer” differs country to country, it seemed much obvious when i moved to Singapore, where Satellite communication and Oil gas Industry dominated while dealing with ISP’s and mobile network operators in Sri Lanka where i was born, studied and improved my skills. Any way in my 1st post, I am going to share my experience with the largest project i have handled, the (value is around 1 million USD), and will share it how i succeeded my 1st massive task.
Every project starts with bidding stage. Bidding (Estimating projects) is another interesting topic to be involve as an Engineer.(will be explained in another detailed post).Normally client gives a specification document (majorly technical and financial )in order to clarify their requirement and we have to present how we are going to satisfy the requirement with complying. It’s like a gambling, as every competitor try to take the bid and so it shouldn’t be an over budgeted and must pass the client’s technical requirement, most importantly it shouldn’t be loss for the company. Luckily this was done by the managing director and a lot of modifications have been done when i was handled the project. Some terms were very disadvantageous for us, any way we got the job. So we are going to do it..
1st thing i have to be more familiar with power supplier units and Alcatel-Lucent equipment, most interestingly to design a customized version which will be most suitable for the Sri Lankan Environment. The unit composed with several items
- Equipment Space- Space for the units to mount in 19″ rack (measured in “U”)
- Rectifier unit ( with rectifier modules n+1 redundancy)
- DCPDU- DC Power Distribution Unit-LLVD and BLVD configuration
- Air conditioning procedure- Heat Exchanges/ Free cooling/Force cooling with Fans
- Battery backup for the vendor equipment
- Proper grounding & surge protection- AC/DC surge protectors
- User friendly/cabin should removable for easy maintenance or to carry to roof top
- Alarm configuration (door/heat/smoke/rectifier failure /power failure etc.)
- Proper wiring system, complying IEC standards.
The above picture shows the sampling unit that we made with a vendor potevio international company, http://www.potevio.com/en ,the sketch was designed by myself deeply going through designs with Huawei, Elteck, and Delta, which were more convenient models exist with telecom vendors, but found some issues with Sri Lankan conditions. The most important fact that I noticed is, environmental condition. In urban areas, there is a big problem with air quality, with dust and, near by the sea, it will affect corrosion effect and malfunctioning of node equipment due to salty mist and dust. So we proposed to the client the heat removal mechanism should not be air to air or force cooling using Centrifugal fans, but from heat exchanges or a hybrid mechanism (DC Air condition + Heat Exchanges).Using Heat Exchanges , we can get main 2 advantageous, as from its mechanism it creates a sealed environment inside the cabin and it prevents salty air in coastal areas or dusty air at urban areas to affect .Considering power consuming the Energy Efficient ratio is very high in heat exchanges (power consumption of heat removal equipment should be less to maintain less down time) and our proposed model was heat exchanges. But due to budgetary issues we were able to negotiate with the client only with portion of set to apply this.
Considering equipment space, we got it from the client that they need 15U space for model 1 with heat exchanges and 10U space for the model with Fan cooling system(1U=44.45mm) Then we needed the maximum DC current needed to calculate how many rectifiers to set. Basically from my experience for a IDU( Indoor unit in microwave Links) needs 1-2 DC Amps, where BBU needs 5-10DC Amps in normal operation, discussing with client they confirmed to set 100A max DC output for the node, so in rectifier selection , we need N+1 redundancy, so we use 50Ax3 units (( 100/50)= 2+1(redundancy)=3). Other main thing regarding DC power distributing, we have to differentiate critical and non-critical loads in a power distribution, normally in mobile telecommunications MW link power feed via critical load , and others ( BTS load, 3G/4G BBU loads ) in non-critical loads. This scenario we discussed with the client and negotiated how much DC load needed for a critical power from total power and able to finalize the distribution unit loads in common for all nodes.
In my next post i will discuss about Battery bank selection, cable selection inside cabin, rectifier placement in the cabinet, cabinet separation, how to optimize space in the cabinet and surge protection devices selection, and internal cabin manufacturing.
- BTS- Base Transceiver Unit
- BBU- Base Band Unit
- DCPDU-DC Power Distribution Unit
- ISP-Internet Service Provider
- LLVD-Load Low Voltage Disconnect
- BLVD-Battery Low Voltage Disconnect