Trial of Super High Efficiency Rectifiers (98%) in Telecom Networks

Paul Eve*, Fernando Ruiz Gomez**, Eddie Gao** *British Telecom

**Huawei Technologies CO, Ltd paul.eve@bt.com fernando.ruiz@huawei.com gaohuanyuan@huawei.com

Abstract - BT has a long term commitment to

reduce its carbon impact. In line with BT’s energy & carbon strategy and to develop further a rectifier re-placement programme currently underway in the BT UK network, a trial of Huawei’s super high efficiency rectifier within a BT operational site is to be imple-mented.

Keywords: Rectifier Replacement, Super High Effi-ciency Rectifiers, Energy Efficiency, Live sites trial

Building upon the success of the replacement project, driven by BT in partnership with Huawei where 23,400 legacy power systems are in scope [2], it became a natural step to extend this project and the corresponding ROI analysis to include the newly launched super high effi-ciency unit from Huawei. This new rectifier has a maximum efficiency of 98% and more than 96% when the load rate is above 20%. This ef-ficiency performance makes the new unit very attractive to use in applications where energy consumption is a crit-ical issue, particularly in an application where installa-tions containing old inefficient technology are being tran-sitioned to modern technology. This paper introduces the new super high efficiency recti-fier and also the implementation of the trial performed in one specific site within BT’s network

I. BACKGROUND

Suppliers View - Information and Communication Tech-nologies (ICT) have been growing and will continue to grow in an astonishing speed. The ICT industry continues to be challenged by the rapidly increasing demand for mobile data. As a result, the development of mobile infra-structure will accelerate in the next coming years. It is therefore clear that the e-business/ICT revolution will have a negative impact on the environment. Green ICT is Huawei Energy vision and it’s the source of inspiration in the development of all company products. It became therefore a natural step for the R&D team to im-prove further the state of the art efficiency of telecom rec-tifiers from 96% to 98%. Operators View - With the rectifier replacement pro-gramme underway in BT, and with awareness of advances in Huawei’s rectifier technology offering, BT wished to review potential Return On Investment (ROI) impact if transition was made to deploy the new 98% super high

efficiency product instead of the current 96% high effi-ciency product. Further improvements to energy efficien-cy operation of the BT network being in line with BT’s strategy to reduce carbon impact. Should analysis of tran-sition to Huawei’s super high efficiency rectifier product also indicate an improved ROI then this would be a win win situation for BT with respect to carbon reduction strategy and optimised network investment and operation costs.

II. INTRODUCTION OF HUAWEI’S SUPER HIGH EF-FICIENCY RECTIFIER

The rectifier is a key component of telecom equipment power supply systems. Incorporating a number of patent-ed technologies including MPII, high efficient topology, MEPK, intelligent algorithm and MSHT, heat dissipation technology; the latest generation of Huawei rectifiers can achieve a peak conversion efficiency of 98%. At 98% conversion efficiency, this rectifier can further reduce conversion power loss by 50% compared to a mainstream rectifier in the industry. The rectifier’s higher efficiency reduces heat dissipation, leading to improved power density as well as a 40% pow-er failure rate reduction and a lowered noise level. In ad-dition, this new unit is keeping the same power density, 42.7W/inch3 as for the previous generation, saving the same amount of cabinet space and footprint as before.

Figure 1. R4850S, The Super high efficiency rectifier

from Huawei

III. SINGLE UNIT PERFOR-MANCE VALIDATION

The performance of this super high efficiency rectifier was validated by BT during a test performed in Huawei’s Headquarters in Shenzhen. Two units from a pre-series were randomly picked-up for this test.

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978-1-4799-3104-0/14/$31.00 ©2014 IEEE

The efficiency and the important parameters of the overall performance of this unit were measured. THD and the values of the output ripple, including the psofometric noise, were in the same range as those measured on the previous generation of rectifiers from Huawei. The peak efficiency was as expected, slightly above 98%, as it can be seen in fig 4.

Figure 4. Measured efficiency, single unit

The efficiency of this unit was validated at VDE previ-ously; the results of those measurements are shown in figure 5 below.

Figure 5. VDE Report

The efficiency measured by VDE validates the measure-ment performed in Huawei’s Headquarters and is in ac-cordance with expectations.

IV. SYSTEM PERFORMANCE VALIDATION

The next step of this trial was to validate the performance of this rectifier, especially the efficiency, in a system powering a live network. The chosen site for this trial was Unit D (digital switching unit) in BT’s Bexleyheath Cen-tral Office, Kent, England. The reason for choosing this site was that we had historic efficiency measurements available both with the systems fitted with legacy rectifi-ers, but also using the high efficiency (96%) units. This could give us an opportunity to make a comparison of the measured performance of both generations of rectifiers. The power analyzer used for those measurements was the same as for the measurements performed previously, Yokogawa’s WT3000 [2], but instead of using split-core transformers for the measurement of all currents, as we did before; current measurement devices MACCplus from Hitec were used to measure the AC-currents instead. Only for the measurement of the output current a HT1000 split-core transformer was used as we couldn’t break the path of the load current when installing the current sensor. We believe that by using these devices, the total accuracy of our measurements was enhanced due to the improved ac-curacy of the MACCplus sensors, as illustrated in the cal-ibration report shown in Fig. 6.

90.000

91.000

92.000

93.000

94.000

95.000

96.000

97.000

98.000

99.000

4% 16% 28% 36% 46% 56% 68% 84% 92% 98%

Efficiency

Output Power(%)

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. Figure 6. Calibration report of MACCplus current sensors A challenge that came up using the MACCplus devices was that we needed to disrupt the current path on the AC-cables in order to connect the sensors. As any interruption of service to BT’s customers was unacceptable, and also considering that we could connect two rectifiers per phase in the existing installation, we just added as many 50A units (in one or two phases) needed to support the load. This allowed us to disconnect the remaining phase in or-der to add the current sensor. Once that phase was ready, we could move two 50A rectifiers to it and proceed to disconnect the other two phases, one at a time, in order to connect the remaining sensors. We performed the measurements once all the current sen-sors were in place. As we had more accurate measurement equipment available we also took the opportunity to re-measure the efficiency of the currently deployed 96% technology rectifiers. Fig 7 below illustrates the measurement set-up including the current sensors.

Figure 7. Measurement equipment and set-up

In the table 1 below, the results of our new measurements are additional to those measured before on the legacy sys-tems [2]. We can then make a comparison of the original efficiency measured to what we obtained using the super high efficiency rectifiers. System (PER No.)

Output current (A)

• Legacy equip-ment (%)

• Average

(%)

• Huawei Super High Efficiency

Improve-ment (%)

0 70,56 87.005 85.54 97.21 11.67

1 27.7 84.076 2 62.11 88.413

85.43

96.90

11.47 3 70.83 84.817 8 33.46 83.062 4 76.17 87.592

86.93 97.18 10.25 5 63.0 88.47 6 65.15 84.743 7 (RCAB)

15.99 78.608 78.61 Not meas-ured

NA

Table 1. Results of efficiency measurements

The reason of why the RCAB-system was not measured this time was that considering BT’s dimensioning rules, we needed to put two units in the system and we believe that it’s not efficient to use two 50A rectifiers (N+1 con-figuration) when the load current is only around 16A. For lightly loaded systems, the best solution is to consolidate, as has been implemented during the BT replacement pro-gram. A comparison of the results obtained with the new super high efficiency rectifiers to the efficiency measured on the standard 96%-ones is shown in table 2 below.

System (PER No.)

Output current (A)

• Huawei High Efficiency

• Huawei Super High Efficiency

Difference (%)

0 70,56 95.58 97.21 1.63

1 27.7 2 62.11

95.72

96.90

1.18 3 70.83 8 33.46 4 76.17

95.80 97.18 1.38 5 63.0

Table 2. Comparison of efficiency

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The improved efficiency using super high efficiency recti-fiers was between 10.25 to 11.67 % compared to BT’s legacy network rectifiers, which is 1.18 to 1.63% higher than using 96% units.

V. BENEFITS OF A REPLACE-MENT PROGRAM USING SU-PER HIGH EFFICIENCY REC-TIFIERS

Transition to deploying super high efficiency rectifier products offers the main benefit of reducing further power conversion losses when powering BT’s legacy network, and opportunity to use the new product for new build ap-plications within BT. Further reduction of power conver-sion losses also offers further benefit for reduced cooling power consumption demand. Other benefits described in section IV of reference document [2]can be updated as follows following experience of programme roll-out in BT:-

• Network powering consumption reduction – Average consumption following conversion and consolidation has been proved in line with ex-pectations with a typical 10-12% improvement. Reduced power system conversion losses also resulting in the anticipated cooling system con-sumption reduction.

• Power system consolidation – Consolidation of

power systems has been a key focus through im-plementation phases to date, achieving an aver-age consolidation ratio of greater than 3:1.

• Battery Consolidation – Consolidation of pow-er systems allows better utilisation of battery as-sets. Forecast was a 15-20% reduction in battery assets. Experience to date through roll-out phas-es is 23%+.

• Scrap metal sale – Negligible benefit through

scrap metal disposal.

• Opex reduction – Better than anticipated sys-tems consolidation, 5 year warranty and increase from 3 year to 5 year proactive maintenance pe-riodicity is exceeding Opex reduction estimates.

• Solution average pricing – Outturn actuals low-

er than estimated costs exceeding ROI estimates.

VI. ROI COMPARISON

At the time of wiring this paper in excess of 2,500 legacy power systems have been upgraded within the BT net-work. Clarity therefore exists with respect to achieved av-erage deployment costs. When assessing potential addi-tional benefit through transition to super high efficiency rectifier products for subsequent deployment phases there

is certainty on base pricing upon which analysis can be made for transition opportunities. Figure 8 below indicates the ROI profile of the whole programme based upon established deployment costs us-ing 96% efficiency rectifier technology. Figure 9 shows the impact on the 5 year programme if use of 98% rectifi-er technology at commencement is considered. Note a 3 month improvement in ROI is indicated for transition to super high efficiency rectifier technology if the whole programme is considered.

Figure 8. 5 year programme view - 96% technology

Figure 9. 5 year programme view - 98% technology

Figure 10 below considers a single year ROI view using 96% efficiency technology compared to figure 11 giving a view of one year ROI where 98% super high efficiency technology deployment is considered. A 1 month im-provement in ROI of 2.5 years.

ROI Month 31

ROI Month 55

ROI Month 52

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Figure 10. 1 year programme view - 96% technology

Figure 11. 1 year programme view - 98% technology

If we consider longer term savings differential between use of 98% technology compared to 96% it can be demonstrated that appreciable additional savings can be achieved. With reference to figure 12 which considers cumulative savings over 5+ year’s use of 98% technology products achieves £9M more savings than using 96% technology. The savings takes in to account the purchase price differential between the two product types.

Figure 12. Cumulative savings comparison – 96% vs 98%

Technology product

VII. CONCLUSION

This paper describes the technology offering super high efficiency 98% rectifier products, their trial in a live net-work application and the impact of the new technology to return on investment. In the live trial the new products offer an efficiency improvement of 10-12% depending on individual power system loading and hence rectifier utili-sation, this being a typical 1.4% improvement compared to existing high efficiency product. Use of the super high efficiency rectifier at indicative price points offers an improvement to ROI (2.5 years for 1 year investment view) and can therefore be concluded as a success for proving the new technology, offering best in class network operation costs and reducing carbon emission to lowest possible level.

Where longer term savings are considered beyond initial ROI break-even point the 98% technology offers signifi-cantly greater long term savings. In the modelling within this paper over a 5 year period circa £9M additional are indicated (more than 13% greater savings compared to 96% technology). Use of super high efficiency products therefore makes a good business case for BT to utilise this new product for the remainder of BT’s legacy network transformation programme.

References

[1] P. Eve, C. Duan, Z. Li A. Na “Innovative Rectifier Modernization Technologies for Legacy Power Effi-ciency Improvement” Telecommunications Energy Conference (INTELEC), 2012 IEEE 34th International

[2] P. Eve, F. Ruiz Gomez, C. Duan, A. Na “Imple-mentation of Innovative Rectifier Modernization Technologies for Efficiency Improvement” Telecom-munications Energy Conference (INTELEC), 2013 IEEE 35th International

ROI Month 30

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