**3. The construction of Al-Zawia combined cycle power plant and its connection with the power system grid**

Al-Zawia CCPP contains of three steam turbines and 6 gas turbines, beside two auxiliary motor turbines. The six gas turbines are known as (GT11, GT12, GT13,

*Assessment of Power Plants in the Western Region of Libya during a Period of Insecurity DOI: http://dx.doi.org/10.5772/intechopen.97208*

GT14, GT15 and GT16), whereas, the steam turbines are called (ST10, ST20 and ST30). The auxiliary motor turbines named (TM05 & TM10). The nine units of steam and gas are divided to three compounds, each compound contains two gas turbines coupled with steam turbine [4].

Al-Zawia CCPP is connected to the general power system grid through eight electric circuits to transfer the produced energy. There are two main transmission lines 400 KV and the rest are 220 KV. Four transmission lines are linked to Western Tripoli power plant. The 400 KV transmission lines need to reduce the transferred energy to 220 KV using step-down transformer 400KV/220 KV, and the other two 220 KV transmission lines are linked directly to the Bus-Western Tripoli 1 &2 respectively. The fifth and sixth transmission lines 220 KV are connected to Al-Harsha substation through Bus Al-Harsha 1 &2. The last two transmission lines 220 KV are joined with Zahra Gas Turbine power plant.

From **Figure 2**. it can be noticed that the annual energy produced from Al-Zawiya PPCC for the year 2019 is fluctuating and not constant in all months of the year. The best performance for Al- Zawiya PPCC was in the winter season, specifically in January, where it reached 884274 MWh, then it declined by 19.30% In February, where it reached 731551 MWh. August 2019 was the most difficult period of the year for the power plant in a matter of production. Due to the increased energy demand, in the summer season, with the rise of temperatures, the power plant production decreases as well as its efficiency by 55.3% compared to January. Only 394,491 MWh were produced by the power plant during this month which means a very sharp drop in the power plant's production, which is expressed by the plant's inability to produce steadily and continuously. One of the main reasons that led to deficiency production of power plant in August, the worst at all, is the frequent blackouts. There were eight blackouts during this month, in particular, from 02 to 08 to 12–08-201. 4th -August was the worst day ever, where three blackouts took place within a 24-hour. In the following figures (**Figures 3**–**5**), there are more details on the power plant's performance in some of these days [8].

The daily report of Al-Zawia CCPP shows the status of the nine units on the day of blackout, as following; the GT11 and GT12 were tripped at 10:17 on 02/08/2019 due to a shake in the grid. The GT11, GT13, and GT12 were restored at 12:51, 13:16, and 14:05 consequently. The GT13 tripped at 14:07 due to a shake in the grid and it was restored at 14:29, then, it tripped again at 15:39 for the same previous reasons. The GT12 tripped again at 15:39 due to a shake in the grid. The

**Figure 2.** *The total produced energy by Al-Zawia CCPP in 2019.*

**Figure 3.** *The produced energy by Al-Zawia CCPP on 02-08-2019.*

#### **Figure 4.**

*The statu of the nine units on the day of blackout 03-08-2019.*

GT11, GT15, and GT16 tripped because of a shake in the grid, which let to blackout at 16:52. TM 05 and the GT14 were restored at 21:00, 21:59 respectively. Once again, a complete Blackout At 22:34, and TM 05 stayed disconnected.

As result of the repeated blackouts, it can be shown in **Figures 3**–**6** the sharp decline of the daily produced energy by the six gas units, and not to mention that the three steam units were all out of service.

On the day after 03-08-2019, the scenario of the blackout continued until, the gas units were started up one by one as following; GT14 at 18:12, GT15 at 18: 18, GT11 at 18:35, GT16 at 18:56, and GT12 at 19:38. On the day after 03-08-2019, the scenario of the blackout continued until, the gas units were started up one by one as following; GT14 at 18:12, GT15 at 18: 18, GT11 *Assessment of Power Plants in the Western Region of Libya during a Period of Insecurity DOI: http://dx.doi.org/10.5772/intechopen.97208*

**Figure 5.** *The produced energy by the units of Al-Zawia CCPP on of the day of the blackout 4-8-2019.*

**Figure 6.** *The performance of gas units of Al-Zawia CCPP on one day of the blackouts 07-08-2019.*

at 18:35, GT16 at 18:56, and GT12 at 19:38. At the same day, at 20:20 another blackout was occurred. The gas units were started up in order GT12 22:08, GT11 at 22:43, GT14 at 23:04, GT15 23:59 and GT16 00:17. In the third day in row,

#### **Figure 7.**

*Comparative of the total produced energy on normal operation day and on the days of the blackouts.*

**Figure 8.**

*Comparative of the total efficiency on normal operation day and on the days of the blackouts.*

*Assessment of Power Plants in the Western Region of Libya during a Period of Insecurity DOI: http://dx.doi.org/10.5772/intechopen.97208*

on 04-08-2019 at 02:32 all gas units were shut down again which means blackout again.

After a long exhausting night of continuous and tedious work from the plant's engineers and operators to restore the units to the network, they succeeded to restore four out of six respectively, GT14 at 11:45, GT12 at 12:10, GT15 at 12:30 and GT16 at 12:50 on 04-08-2019. After 1.16 h, the restored units went blackout again. In the evening, the four gas units were successfully restored within 1.10 h, as following, GT12 at 20:45, GT14 at 20:55, the GT16 at 21:30, and GT15 at 21:55″. Within 24 hours, the third blackout occurred at 22:28. On 05-08-2019, On 05-08-2019, the swinging four units were restored and connected to the power system grid again in order, the GT16 at 01:05, GT14 at 01:15, GT15 at 1:37, and GT12 at 03:40. In the morning at 09:07, a blackout took place again.

On 07-08-2019 at 13:56 another blackout occurred. 03:31 hours later, four gas units were restored in sequence GT14 at 17:25, GT15 at 19:08, GT16 at 17:34, and GT11 at18:06.

From next **Figures 7** and **8** it can be noticed the following; the increase of the daily total produced energy by Al-Zawia CCPP at the beginning of the year 2020 compared to the year before. The sharp decrease in operating efficiency in the days of blackouts compared to the normal operation days.

## **4. Western Mountain power plant**

Western Mountain Power Plant (Ruwais) is located southwest of the capital Tripoli, with an estimated distance of about 250 km. It depends on natural gas to produce electricity as the main fuel, and on diesel as fuel in case of emergency. It consists of four units as a basic project and two units as an expansion project, meaning the total is six units, each unit produces 156 MW, which means 936 MW total. There is a Central Control Room (CCR) through which all units can be controlled, and each unit can also be controlled through Power Control Center (PCC) sub-controller.

For the connection with GECOL power system, there are six units (GT11, GT12, GT13, GT14, GT15 and GT16). The first four units GT1- GT4 are connected to transmission lines 220 KV through step-up transformers. There are five transmission lines 220 KV, the first and second lines are connected to Shakshuk substation and known as "Shakshuk1 and Shakshuk2". The third and fourth lines are linked to Al-Rabeta, Zahra substations respectively, and the last line is connected to Tataouine – Tunisia photovoltaic 10 MW. The fifth and sixth units (GT5, GT6) are connected to a 400 kV high voltage line via step-up transformer and linked with Ghadames substation.

**Figure 9** shows the total produced energy from natural gas by the six units of the Western Mountain power plant, the consumed energy from natural gas, and the total available loads in 2019. It can be seen the variation of the six units in the amount of annual production energy. It can be noticed that the sixth and second units are considered the best in terms of performance. They produced 945001.25 MW and 861 103.80 MW respectively. While the fourth and first units are the worst in terms of the amount of electrical energy production, the reasons behind are; the units exceeded the equivalent operating hours for overhaul and that the last one for GT14 was on 5 July 2016, as well as, the number of scheduled stopping hours were 2288.23 hours as shown in **Table 1**. As for the first unit GT11, the last overhaul was on 23 November 2015, and the hours of sudden stop were 2990.6 hours, which explains the reason for the low amount of energy production compared to other units [9].

**Figure 9.**

*The total produced energy by the six units of the Western Mountain power plant in 2019.*


#### **Table 1.**

*Annual report on the number of operating hours of the Western Mountain power plant in 2019.*

**Figure 10** shows the total energy produced from the six units of the Western Mountain power plant for the year 2020. There is a significant increase for production of the GT11 compared to the year 2019, which reached 35% from its production. The same applies to GT14 and GT15 whose performance improves by 21.5% and 20.01%, respectively. There is a slight decrease in the production quantity of the GT16. The rise of energy production by GT11 goes to the increase of the number of actual operating hours from 5598.02 in 2019 to 8394.45 in 2020, as well as the decrease in the number of scheduled stoppage hours from 171.1 in 2019 to 67.11 in 2020, as shown in **Tables 1** and **2**.

**Figure 11** shows the significant improvement in the performance of the Western Mountain power plant through the increase in energy production and the amount of *Assessment of Power Plants in the Western Region of Libya during a Period of Insecurity DOI: http://dx.doi.org/10.5772/intechopen.97208*

#### **Figure 10.**

*The total produced energy by the six units of the Western Mountain power plant in 2020.*


#### **Table 2.**

*Annual report on the number of operating hours of the Western Mountain power plant in 2020.*

energy sent to consumers in 2020 compared to the year before. This improvement has achieved because of; in the first quarter of 2020, the civil war stopped in the capital, Tripoli, where the National Control Center Tripoli of GECOL, some main transmission lines, substations, and Tripoli South Power plant are on the armed conflict area "south of Tripoli". This puts this equipment under the risk of destruction, damage, and cutting off some main transmission lines. As result, these risks effect on the stability of the power system grid and cause of frequent outages and blackouts.

Due to the high temperatures in summer season, specifically in August, which causes an increase of electricity demand by customers. Those conditions, put the power plants under the pressure to cover the increase of energy demand. This month was chosen to study the performance of the six units of the Western Mountain power plant under these conditions. **Figures 12**–**17** show the performance of the six units GT11, GT12, GT13, GT14, GT15 and TG16 in terms of maximum, minimum and average loads.

#### **Figure 11.**

*Comparative of Western Mountain power plant production between 2019 & 2020.*

#### **Figure 12.**

*The performance of GT11 in Aug-2020.*

From **Figure 12**, it can be seen that the minimum loads in GT11 decreased sharply twice in August, the first one was on 10-Aug-2020 due to over frequency as reported on the recorded data, which led to the trip of GT11 0.5 h. The second sharp decline was on 19-Aug-2020 for the same reason and caused an outage of 1.9 h.

The minimum loads of GT12 decline suddenly to zero four times as shown in **Figure 13**. Which means four outages, the first sudden decline was on 03-August −2020 because of a trip of GT12 due to surge protection. The second and third decline was on 10 & 19 -Oct led to a trip of GT12 due to over frequency. Tripped of GT12 on 29- Aug due to the high temperature of the turbine outlet caused the last sharp decline.

There were sharp decreases in the remaining four units GT13 and GT16, as shown in **Figures 14**–**17**. The units GT13 &GT15 declined to zero minimum loads three times in Aug- 2020, which mean three interruptions, while the GT14 was the worst among the six units s in terms of performance and quantity of production. The minimum loads of GT14 decreased to zero six times in a period 9–26 Aug, which shows the clear effect of lack of maintenance. The GT16 was the best performance compared to the other units even, the minimum loads reduced zero twice in the same period.

*Assessment of Power Plants in the Western Region of Libya during a Period of Insecurity DOI: http://dx.doi.org/10.5772/intechopen.97208*

**Figure 13.** *The performance of GT12 in Aug-2020.*

**Figure 14.** *The performance of GT13 in Aug-2020.*

**Figure 15.** *The performance of GT14 in Aug-2020.*

**Figure 16.**

*The performance of GT15 in Aug-2020.*

**Figure 17.** *The performance of GT16 in Aug-2020.*

The cause of interruptions in GT14 is due to the following: four interruptions to increased frequency, the fifth programmed for maintenance, and the sixth interruption because of repairing air leakage. The units GT15 &GT16 were tripped twice on 10 &19 – Aug, due to over frequency. From all **Figures 12**–**17**, it can be noticed that all units were tripped on 10 & 19 -Aug, except, GT14 due to over frequency and shake in the power system grid.
